follow CCP

Recent blog entries
popular papers

What Is the "Science of Science Communication"?

Climate-Science Communication and the Measurement Problem

Ideology, Motivated Cognition, and Cognitive Reflection: An Experimental Study

'Ideology' or 'Situation Sense'? An Experimental Investigation of Motivated Reasoning and Professional Judgment

A Risky Science Communication Environment for Vaccines

Motivated Numeracy and Enlightened Self-Government

Ideology, Motivated Cognition, and Cognitive Reflection: An Experimental Study

Making Climate Science Communication Evidence-based—All the Way Down 

Neutral Principles, Motivated Cognition, and Some Problems for Constitutional Law 

Cultural Cognition of Scientific Consensus

The Tragedy of the Risk-Perception Commons: Science Literacy and Climate Change

"They Saw a Protest": Cognitive Illiberalism and the Speech-Conduct Distinction 

Geoengineering and the Science Communication Environment: a Cross-Cultural Experiment

Fixing the Communications Failure

Why We Are Poles Apart on Climate Change

The Cognitively Illiberal State 

Who Fears the HPV Vaccine, Who Doesn't, and Why? An Experimental Study

Cultural Cognition of the Risks and Benefits of Nanotechnology

Whose Eyes Are You Going to Believe? An Empirical Examination of Scott v. Harris

Cultural Cognition and Public Policy

Culture, Cognition, and Consent: Who Perceives What, and Why, in "Acquaintance Rape" Cases

Culture and Identity-Protective Cognition: Explaining the White Male Effect

Fear of Democracy: A Cultural Evaluation of Sunstein on Risk

Cultural Cognition as a Conception of the Cultural Theory of Risk


Shockingly sad news . . . 

A model of models for the good life of being a scholar . . . .


Geoengineering & the cultural plasticity of climate change risk perceptions: Part I


 Yesterday I posted a small section of a CCP paper, scheduled for publication in the Annals of the American Academy of Political & Social Sciences, that reports the results of a study on how emerging research on and public discussion of geonengeering might affect the science communciation environment surrounding climate change.

I’ve been thinking of geoengineering again recently, mainly because on my trip to Cardiff University I got a chance to discuss public attitudes toward it—existing and anticipated—with Nick Pidgeon, who along with Adam Corner and other members of the Cardiff Understanding Risk Group, has been doing some great studies of this topic.

How the public will perceive geoengineering is fascinating for all kinds of reasons, but the one that I find the most intriguing is geoengineering’s inversion of the usual cultural meanings of climate change risk. 

According to the cultural cognition thesis, we should expect persons who are relatively hierarchical and individualistic to be climate change skeptics: crediting evidence of the dangers posed by human-caused climate change implies that we should be restricting commerce, industry, markets, and other forms of private orderings—activities of extreme value, symbolic as well as material, to people with these outlooks.

By the same token, we should expect persons who are egalitarian and communitarian to be highly receptive to evidence of the danger of climate change: because they already are morally suspicious of commerce, industry, and markets, to which they attribute unjust social disparities (actually, they might like to take a look at the disparities that existed in pre-market societies & figure out which ones were greater, but that’s another matter!), they find it congenial to see those activities as sources of danger that ought to be restricted.

This is the plain vanilla rendering of Douglas & Wildavsky’s “cultural theory of risk” (I don't actually buy it, to tell you the truth!)—and, indeed, Wildavsky, who died in 1993 (at the early age of 63), had already characterized global warming as “the mother of all environmental scares”:

Warming (and warming alone), through its primary antidote of withdrawing carbon from production and consumption, is capable of realizing the environmentalist’s dream of an egalitarian society based on rejection of economic growth in favor of a smaller population’s eating lower on the food chain, consuming a lot less, and sharing a much lower level of resources much more equally. 

But Wildavsky—a mainstream political liberal whose experience with the radical “free speech” movement at Berkeley left him obsessed with the “rise of radical egalitarianism”—puts a spin on climate change that contravenes the fundamental symmetry of the laws of cultural cognition. 

That is, he seems to imply that it’s only “egalitarian collectivists” who will be motivated to assign to evidence of climate change risks a significance biased in favor of their preferred way of life.

But if, as Douglas and Wildavsky so adamantly insisted in Risk and Culture, “[e]ach form of social life has its own typical risk portfolio”—if  all “people select their awareness of certain dangers to conform with a specific way of life,” and thus “each social arrangement elevates some risks to a high peak and depresses others below sight”—then there's no more reason to expect hierarchical individualists to form reliable perceptions of climate change risks than egalitarian communitarians.

Wildavsky would have come closer to conveying the logic of his and Douglas’s own position, then, if he had called global warming the “mother of all environmental risk-perception conflicts.”

If we follow the symmetry of cultural cognition out a bit further, moreover, we can see that there is in fact nothing inherently “egalitarian” in climate-change belief or inherently “individualistic” in climate-change skepticism.  

Dangers are selected for public concern according to the strength and direction of social criticism,” we are told.  But because what effect acknowledging a particular assertion of risk will have on the stock of competing ways of life is determined not by people's "direct examination of physical evidence" but by their understanding of social meanings (those are what determine for them what the "physical evidence" signifies), all we can say is that in the context of some particular society's "dialogue on how best to organize social relations," acceptance of human-caused climate change just happens to be understood as indicting individualism and vindicating egalitarianism.

But that could change, surely!  

The case of geoengineering shows how. 

The argument for investigating its development—one forcefully advanced by both the U.S. National Academy of Sciences and Royal Society—obviously presupposes both that human-caused climate change is happening and that it poses immense threats to human well-being.

But the cultural narrative of geoengineering is quite different from any of the other proposed responses. Whereas carbon-emission restrictions proclaim the inevitable limits of technological and commercial growth, geoengineering (much like nuclear power) asserts the potential limitlessness of the same.

“We are not like the stupid animals,” the geoengineering narrative says, “who reach the pinnacle/mode of the Malthusian curve and then come crashing down.” 

“We use our intelligence to shift the curve—deploying technology, fueled by commerce and markets, to successfully repel the very threats to our well-being that are the byproducts of commerce, markets, and technology! Brilliant!

“It used to be said,” the geoengineering narrative continues, “that the natural population density of a city like, say, London, was  shy of 4,000 persons per mile—because at around that point people would inevitably die in droves from ingesting their own shit (literally!).”   “But we invented modern systems of sewage and water treatment—we used our ingenuity to shift the curve—and now we can have cities (London: 12,000/mile; Sao Paulo 20,000/mi) many many times more dense then that!”

“Well,” the narrative concludes, “the time has come again to shift the curve, to use our ingenuity to handle the byproducts of our own ingenuity, to blast our shit into outerspace so that we don’t choke on it! Let’s go!”

This is inspiring to the individualist.

It is demoralizing to the egalitarian.  The “lesson” of climate change, for him or her, is “game over," not “more of the same”; "we told you so!," not "Yes, we can!"

The answer to our “planetary over-indulgence” is a “diet,” not “atmospheric liposuction”!

And because the cultural narrative is demoralizing to the egalitarian, geoengineering is terrifying

The risks form unforeseen and unforeseeable consequences are too high.  After all, the climate is a classic “chaotic” system—one the sheer complexity of which defies the sort of modeling that would have to be done to intelligently manage any geoengineering “fix.”

It will never ever work, and scientists like those in the NAS and Royal Society are being foolish for even proposing to investigate its risks and benefits. Indeed, it's dangerous even to discuss geoengineering, the mere mention of which threatens to dissipate the surging public demand in the U.S. and other industrialized countries to impose a carbon tax and enact other sorts of restrictions on fossil fuel use.

But what if the best available scientific evidence on climate change—including the inevitability of genuinely catastrophic climate impacts no matter what level of carbon mitigation world governments might agree to (including complete cessation of fossil fuel use tomorrow)—suggests that that nothing short of geoengineering can stave off myriad disasters, including continuing rising sea levels, violent and erratic storm activity in various parts of the world, and famine-inducing droughts over much of the rest?

Who should we expect to be skeptical of that evidence? The egalitarian communitarian or the hierarch individualist?

If in considering such evidence, the two could be observed to be trading places on whether the “scientists were biased,” “computer models could be trusted,” “the call for action is premature” etc., would that not be a nice little proof of the cultural theory of risk?

Tune in "tomorrow" & I’ll show you what the results of such an experiment looks like! 


Three models of risk perception -- & their significance for self-government . . .

From Geoengineering and Climate Change Polarization: Testing a Two-channel Model of Science Communication, Ann. Am. Acad. Pol. & Soc. Sci. (in press).

Theoretical background

Three models of risk perception

The scholarly literature on risk perception and communication is dominated by two models. The first is the rational-weigher model, which posits that members of the public, in aggregate and over time, can be expected to process information about risk in a manner that promotes their expected utility (Starr 1969). The second is the irrational-weigher model, which asserts that ordinary members of the pubic lack the ability to reliably advance their expected utility because their assessment of risk information is constrained by cognitive biases and other manifestations of bounded rationality (Kahneman 2003; Sunstein 2005; Marx et al. 2007; Weber 2006).

Neither of these models cogently explains public conflict over climate change—or a host of other putative societal risks, such as nuclear power, the vaccination of teenage girls for HPV, and the removal of restrictions on carrying concealed handguns in public. Such disputes conspicuously feature partisan divisions over facts that admit of scientific investigation. Nothing in the rational-weigher model predicts that people with different values or opposing political commitments will draw radically different inferences from common information. Likewise, nothing in the irrational-weigher model suggests that people who subscribe to one set of values are any more or less bounded in their rationality than those who subscribe to any other, or that cognitive biases will produce systematic divisions of opinion of among such groups.

One explanation for such conflict is the cultural cognition thesis (CCT). CCT says that cultural values are cognitively prior to facts in public risk conflicts: as a result of a complex of interrelated psychological mechanisms, groups of individuals will credit and dismiss evidence of risk in patterns that reflect and reinforce their distinctive understandings of how society should be organized (Kahan, Braman, Cohen, Gastil & Slovic 2010; Jenkins-Smith & Herron 2009). Thus, persons with individualistic values can be expected to be relatively dismissive of environmental and technological risks, which if widely accepted would justify restricting commerce and industry, activities that people with such values hold in high regard. The same goes for individuals with hierarchical values, who see assertions of environmental risk as indictments of social elites. Individuals with egalitarian and communitarian values, in contrast, see commerce and industry as sources of unjust disparity and symbols of noxious self-seeking, and thus readily credit assertions that these activities are hazardous and therefore worthy of regulation (Douglass & Wildavsky 1982). Observational and experimental studies have linked these and comparable sets of outlooks to myriad risk controversies, including the one over climate change (Kahan 2012).

Individuals, on the CCT account, behave not as expected-utility weighers—rational or irrational—but rather as cultural evaluators of risk information (Kahan, Slovic, Braman & Gastil 2006). The beliefs any individual forms on societal risks like climate change—whether right or wrong—do not meaningfully affect his or her personal exposure to those risks. However, precisely because positions on those issues are commonly understood to cohere with allegiance to one or another cultural style, taking a position at odds with the dominant view in his or her cultural group is likely to compromise that individual’s relationship with others on whom that individual depends for emotional and material support. As individuals, citizens are thus likely to do better in their daily lives when they adopt toward putative hazards the stances that express their commitment to values that they share with others, irrespective of the fit between those beliefs and the actuarial magnitudes and probabilities of those risks.

The cultural evaluator model takes issue with the irrational-weigher assumption that popular conflict over risk stems from overreliance on heuristic forms of information processing (Lodge & Taber 2013; Sunstein 2006). Empirical evidence suggests that culturally diverse citizens are indeed reliably guided toward opposing stances by unconscious processing of cues, such as the emotional resonances of arguments and the apparent values of risk communicators (Kahan, Jenkins-Smith & Braman 2011; Jenkins-Smith & Herron 2009; Jenkins-Smith 2001).

But contrary to the picture painted by the irrational-weigher model, ordinary citizens who are equipped and disposed to appraise information in a reflective, analytic manner are not more likely to form beliefs consistent with the best available evidence on risk. Instead they often become even more culturally polarized because of the special capacity they have to search out and interpret evidence in patterns that sustain the convergence between their risk perceptions and their group identities (Kahan, Peters, Wittlin, Slovic, Ouellette, Braman & Mandel 2012; Kahan 2013; Kahan, Peters, Dawson & Slovic 2013).

Two channels of science communication

The rational- and irrational-weigher models of risk perception generate competing prescriptions for science communication. The former posits that individuals can be expected, eventually, to form empirically sound positions so long as they are furnished with sufficient and sufficiently accurate information (e.g., Viscusi 1983; Philipson & Posner 1993). The latter asserts that the attempts to educate the public about risk are at best futile, since the public lacks the knowledge and capacity to comprehend; at worst such efforts are self-defeating, since ordinary individuals are prone to overreact on the basis of fear and other affective influences on judgment. The better strategy is to steer risk policymaking away from democratically accountable actors to politically insulated experts and to “change the subject” when risk issues arise in public debate (Sunstein 2005, p. 125; see also Breyer 1993).

The cultural-evaluator model associated with CCT offers a more nuanced account. It recognizes that when empirical claims about societal risk become suffused with antagonistic cultural meanings, intensified efforts to disseminate sound information are unlikely to generate consensus and can even stimulate conflict.

But those instances are exceptional—indeed, pathological. There are vastly more risk issues—from the hazards of power lines to the side-effects of antibiotics to the tumor-stimulating consequences of cell phones—that avoid becoming broadly entangled with antagonistic cultural meanings. Using the same ability that they reliably employ to seek and follow expert medical treatment when they are ill or expert auto-mechanic service when their car breaks down, the vast majority of ordinary citizens can be counted on in these “normal,” non-pathological cases to discern and conform their beliefs to the best available scientific evidence (Keil 2010).

The cultural-evaluator model therefore counsels a two-channel strategy of science communication. Channel 1 is focused on information content and is informed by the best available understandings of how to convey empirically sound evidence, the basis and significance of which are readily accessible to ordinary citizens (e.g., Gigerenzer 2000; Spiegelhalter, Pearson & Short 2011). Channel 2 focuses on cultural meanings: the myriad cues—from group affinities and antipathies to positive and negative affective resonances to congenial or hostile narrative structures—that individuals unconsciously rely on to determine whether a particular stance toward a putative risk is consistent with their defining commitments. To be effective, science communication must successfully negotiate both channels. That is, in addition to furnishing individuals with valid and pertinent information about how the world works, it must avail itself of the cues necessary to assure individuals that assenting to that information will not estrange them from their communities (Kahan, Slovic, Braman & Gastil 2006; Nisbet 2009).


Breyer, S.G. Breaking the Vicious Circle: Toward Effective Risk Regulation, (Harvard University Press, Cambridge, Mass., 1993).

Gigerenzer, G. Adaptive thinking: rationality in the real world, (Oxford University Press, New York, (2000).

Jenkins-Smith, H. Modeling stigma: an empirical analysis of nuclear waste images of Nevada. in Risk, media, and stigma : Understanding public challenges to modern science and technology (ed. J. Flynn, P. Slovic & H. Kunreuther) 107-132 (Earthscan, London ; Sterling, VA, 2001). 

Jenkins-Smith, H.C. & Herron, K.G. Rock and a Hard Place: Public Willingness to Trade Civil Rights and Liberties for Greater Security. Politics & Policy 37, 1095-1129 (2009).

Kahan, D.M. Cultural Cognition as a Conception of the Cultural Theory of Risk. in Handbook of Risk Theory: Epistemology, Decision Theory, Ethics and Social Implications of Risk (eds. Hillerbrand, R., Sandin, P., Roeser, S. & Peterson, M.) (Springer London, 2012).

Kahan, D.M. Ideology, motivated reasoning, and cognitive reflection. Judgment and Decision Making 8, 407-424 (2013).

Kahan, D., Braman, D., Cohen, G., Gastil, J. & Slovic, P. Who Fears the HPV Vaccine, Who Doesn’t, and Why? An Experimental Study of the Mechanisms of Cultural Cognition. Law Human Behav 34, 501-516 (2010).

Kahan, D. M., Braman, D., Slovic, P., Gastil, J., & Cohen, G. (2009). Cultural Cognition of the Risks and Benefits of Nanotechnology. Nature Nanotechnology, 4(2), 87-91.

Kahan, D. M., Slovic, P., Braman, D., & Gastil, J. (2006). Fear of Democracy: A Cultural Critique of Sunstein on Risk. Harvard Law Review, 119, 1071-1109.

Kahan, D.M., Jenkins-Smith, H. & Braman, D. Cultural Cognition of Scientific Consensus. J. Risk Res. 14, 147-174 (2011).

Kahan, D.M., Peters, E., Dawson, E. & Slovic, P. Motivated Numeracy and Enlightened Self Government. Cultural Cognition Project Working Paper No. 116 (2013).

Kahan, D.M., Peters, E., Wittlin, M., Slovic, P., Ouellette, L.L., Braman, D. & Mandel, G. The polarizing impact of science literacy and numeracy on perceived climate change risks. Nature Climate Change 2, 732-735 (2012).

Kahneman, D. Maps of bounded rationality: Psychology for behavioral economics. Am Econ Rev 93, 1449-1475 (2003).

Keil, F.C. The feasibility of folk science. Cognitive science 34, 826-862 (2010).

Lodge, M. & Taber, C.S. The rationalizing voter (Cambridge University Press, Cambridge ; New York, 2013).

Marx, S.M., Weber, E.U., Orlove, B.S., Leiserowitz, A., Krantz, D.H., Roncoli, C. & Phillips, J. Communication and mental processes: Experiential and analytic processing of uncertain climate information. Global Environ Chang 17, 47-58 (2007).

Nisbet, M.C. Communicating Climate Change: Why Frames Matter for Public Engagement. Environment 51, 12-23 (2009).

Philipson, T.J. & Posner, R.A. Private choices and public health, (Harvard University Press, Cambridge, Mass., 1993).

Spiegelhalter, D., Pearson, M. & Short, I. Visualizing Uncertainty About the Future. Science 333, 1393-1400 (2011).

Starr, C. Social Benefit Versus Technological Risk. Science 165, 1232-1238 (1969).

Sunstein, C.R. Laws of fear: beyond the precautionary principle, (Cambridge University Press, Cambridge, UK ; New York, 2005).

Sunstein, C.R. Misfearing: A reply. Harvard Law Review 119, 1110-1125 (2006).

Viscusi, W.K. Risk by choice: regulating health and safety in the workplace, (Harvard University Press, Cambridge, Mass., 1983).



Democracy and the science communication environment (lecture synopsis and slides)

Gave a talk earlier in the week at Cardiff University, the last stop on my fun "cross-cultural cultural cognition road trip." Cardiff's Understanding Risk Research Group features a '27-Yankees equivalent lineup of risk perception scholars--including Nick Pidgeon, Wouter Poortinga, Adam Corner & Lorraine Whitmarsh (I decided not to use that metaphor during my talk)--who are surrounded by top-notch sociologists studying technology and society. They also have a high-charged group of science communication scholars. I had an amaizing few days there & felt very sad when the time came to leave!
Slides from my talk are here. I can't quite remember how I put things, but it was something like this . . . .

0. What is this “science of science communication”?  The science of science communication can be understood as a remedy for two fallacies.

The first is res ipsa locquitur (“the thing speaks for itself”): the validity of valid science is manifest, making scientific study of it neither interesting nor necessary.

The second is ab uno disce omnes (“from one, learn all”): the scientific knowledge necessary to enable a doctor to meaningfully advise a patient on a complicated treatment decision is the same as the knowledge necessary to enable a science journalist to edify a curious member of the public, an empirical researcher to advise a policymaker, an educator to teach a high school student the theory of evolution, etc.

My remarks are mainly directed at the ab uno fallacy. I want to describe the distinctive species of SSC that is most likely to evade comprehension if one makes the mistake of thinking it’s only one thing. It is also the one that is arguably most important for the well-being of democratic society. 

The aim of this species of SSC is to protect the science communication environment.

1. The puzzle of cultural polarization over risk

Members of the public in the U.S. are highly divided on all manner of fact relating to climate change. So are members of the public in many other nations, including the UK.

There are other risks—from GM foods to nuclear power to gun ownership to vaccination against infection by HPV or other contagious diseases—that fracture the members of some of these socieites but not others.

Not to be struck by the puzzling nature of this phenomenon is to admit a deficit in curiosity. It’s not surprising at all that people with different values would disagree about what to do about a societal risk like climate change or gun possession. But there’s nothing in how much one weights equality relative to wealth, or security relative to liberty, that determines whether the earth is heating up as a result of human activity or whether permitting citizens to carry concealed handguns in public deters violent assaults.

It’s not surprising either that ordinary members of the public would disagree with one another on facts the nature of which turns on evidence as technically complex as that surrounding climate change, nuclear power, or gun control. 

But if complexity were the source of the problem, we’d expect disagreement to be randomly distributed with respect to cultural and political values, and to abate as individuals become progressively more comprehending of science. 

Not so: on the contrary, the most science comprehending members of the public are the most culturally polarized! (At least in the U.S.; I’m not aware of resarch of this sort with non-US samples & would be grateful to anyone who fills in this gap in my knowledge, if it is one).

What’s the explanation for such a peculiar distribution of beliefs—and on facts that not only admit of investigation by empirical means but that have in fact been investigated by expert empirical methods?

2. The cultural cognition thesis

The answer (or certainly a very large part of it) is cultural cognition.

Cultural cognition is a species of motivated reasoning, which refers to the tendency of people to conform their assessment of all manner of information (empirical data, logical arguments, brute sense impressions) to some goal or interest independent of forming a correct judgment. 

The cultural cognition thesis holds that people can be expected to conform their perceptions of risk and like facts to the stake they have in maintaining their connection to and status within important affinity groups.

The nature of these commitments can be measured by various means, including right-left political outlooks, but in our research we ordinarily do so with scales patterned on the “worldview” dimensions associated with Mary Douglas’s “group-grid” framework.

3. Some evidence

Studies conducted by myself and my collaborators have generated various forms of evidence in support of the cultural cognition thesis—and against rival theories that are often used to explain political conflict over societal risks.

a. Cultural cognition of scientific consensus. In one study, we performed an experiment that showed how cultural cognition influenced formation of public perceptions of what expert scientists believe. The results showed that how readily individuals of diverse cultural outlooks identified a scientist as an “expert” on climate change, nuclear power, or gun control depended on whether that scientist was depicted as espousing a position consistent with the one that prevails in the individuals’ cultural groups.

If individuals selectively credit and dismiss evidence of “expert” opinion in this fashion, they will become culturally polarized over what scientific consensus is in disputed issues.  And, indeed, the study found that in all cases the vast majority of subjects perceived that “scientific consensus” on the relevant issue—climate change, nuclear power, and gun possession—was consistent with the one that prevailed in their cultural group.

The study findings were not only consistent with the cultural cognition thesis, but also inconsistent with two alternatives.  One of these attributes political conflict over societal risks to one or another group’s hostility to science. In fact, no group subscribed to a position that it perceived to be contrary to prevailing scientific opinion.

The second alternative explanation sees one or another group as more attuned to scientific consensus than its rivals. But in fact, all groups were equally likely to view as the “consensus” among expert scientists the position contrary to the one endorsed as the “consensus” position by the U.S. National Academy of Science.

b . “Feeling” the heat—and the hurricanes, floods, tornados etc.  A common theme—indeed, the dominant for commentators who derive their explanations from syntheses of general literature rather than by original empirical research—attributes popular conflict over climate change to the public’s overreliance on heuristic, “system 1” as opposed to more reflective, dispassionate “system 2” information processing.

Those who advance this thesis typically predict that individuals will begin to revise upward their perception of the seriousness of climate change risks as they experience climate-change impacts first hand.  “Feeling” climate change, it is argued, will create the emotionally vivid impression that those who form their risk perceptions heuristically will require to start taking climate change seriously.

This prediction is also contrary to the evidence. 

It’s true that individuals’ perceptions of climate-change risk correlate with their perception that temperatures in their area have been increasing in recent years. But their perception of recent local temperatures are not predicted by what those temperatures have actually been.

Rather, they are predicted by their cultural outlooks, suggesting that individuals selectively attend to or recall weather extremes in patterns that reflect their groups’ position on climate change.

Nor do individuals appear to uniformly revise their perception of climate-change risks as they experience significant extreme-weather hardships. A CCP study of residents of southeast Florida found that the number of times a person had been forced to evacuate his or her residence, had been deprived of access to drinking water, had suffered property damage, etc. as a result of extreme weather or flooding had a very modest positive impact on the perceived risk of climate change for egalitarian communitarians—the individuals most culturally predisposed to credit evidence of climate change—but none on hierarchical individualists—those most culturally predisposed to dismiss such evidence.

In other words, people don’t “believe” in climate change when they “see” it; they see it only when they already believe it.

Cultural cognition predicts this—although so does elementary logic, since individuals who experience such events can’t “see” or “feel” the cause of them. What they see extreme weather as evidence of (climate change, tolerance of gay marriage, nothing in particular, etc.) necessarily depends on their assent to some account of how the world works that they are not themselves in a position to verify. And that’s where cultural cognition comes in.

c. Motivated system 2 reasoning. The popular “thinking fast, thinking slow” account of climate-change controversy also implies that the members of the public most disposed to use reflective “system 2” reasoning can be expected to form perceptions of climate risk more in line with scientific consensus. 

Again, the evidence does not bear this claim out.   In fact, they are the ones who are the most polarized.

That’s what the cultural cognition thesis tells us to expect.  Those who possess the skills and habits of mind necessary to critically evaluate complex arguments and data have more tools at their disposal to fit their assessments of evidence to the beliefs that are predominant in their identity-defining groups.

4. A polluted science communication environment

The spectacle of intense, persistent political conflict can easily distract us from the state of public opinion on the vast run of facts addressed by decision-relevant science. The number of risk issues that divide members of the public along cultural lines is infinitesimal in relation to the number that don’t but could.  There’s no meaningful level of political contestation over the health risks of unpasteurized milk, medical x-rays, high-power transmission lines, fluoridated water, etc. On these issues, moreover, culturally diverse individuals do tend to converge on the best-available evidence as their capacity for science comprehension increases.

The reason that these issues do not provoke controversy, moreover, is not that individuals understand the scientific evidence on the relevant risks more completely than they understand the evidence on climate change or nuclear power or the HPV vaccine or gun control.

Individuals (including scientists) align themselves appropriately with a body of decision-relevant science much vaster than they could be expected to comprehend or verify for themselves. They achieve this feat by the exercise of a reliable faculty for recognizing insights that originate in the methods that science uses to discern the truth.

Their everyday interactions with others who share their cultural worldviews are the natural domain for the use of this faculty.  Individuals spend most of their time with others who share their values; they can exchange information with them readily, without the friction that might attend interactions with individuals whose fundamental outlooks on life differ fundamentally from their own; and they are more able to read those with whom they share defining commitments, and thus to distinguish those of their number who know what they are talking about from those who don’t.

All the various affinity groups within which individuals exercise their knowledge-recognition faculties are amply stocked with people high in science comprehension, and all fully equipped with high-functioning processes for transmitting what their members collectively know of what’s become collectively known through science. So while admittedly (even regrettably) insular, the ordinary interaction of ordinary individuals with those who share their cultural worldviews generally succeeds in aligning individuals’ beliefs with the best available evidence relevant to the decisions they must make in their personal and collective lives.

This process breaks down only in the rare situation when positions on particular issues become entangled in antagonistic cultural meanings, effectively transforming them into badges of membership in and loyalty to one or another competing group. At that point, the stake that ordinary individuals have in forming and persisting in beliefs consistent with others in their group will dominate the stake they have in forming beliefs that reflect what’s known to science: what she personally believes—right or wrong—about climate change, nuclear power, and other societal risks won’t have any impact on the level of risk she or anyone else faces; the formation of a belief at odds with the one that predominates in her group, however, threatens to estrange her from those on whom her welfare—material and psychic—depends.

These antagonistic cultural meanings are a form of pollution in the science communication environment.  They literally disable the ordinarily reliable faculty ordinary individuals rely on to discern what’s known by science.

Engaging information in a manner that reflects their individual interest in forming and persisting in group-convergent beliefs, diverse citizens are less likely to converge on the best available evidence relevant to the health and well-being of them all.

The factual presuppositions of policy choices having become symbols of opposing visions of the best life, debates over risk regulation become the occasion for illiberal forms of status competition between competing cultural groups.

This polluted science communication environment is toxic for liberal democracy.

 5. The science of #scicomm environment protection

The entanglement of positions on societal risk in culturally antagonistic meanings is not a consequence of immutable natural laws or historical processes.  Specific, identifiable events—ones originating in accident and misadventure as often as strategic behavior—steer putative risk sources down this toxic path. 

By empirically investigating why a putative risk source (e.g., mad cow disease or GM foods) took this route in one nation but not another, or why two comparable risk sources (the HPV vaccine and the HBV vaccine) travelled different paths in a single nation (the U.S.), the science of science communication enables us to understand the influences that transform policy-relevant facts into divisive markers of group identity.

The same methods, moreover, can be used to control such influences.  They can be used to forecast the likely development of them in time to enable actors in government and civil society alike can act to avoid their occurrence. They can also be used to formulate and test strategies for disentangling positions from antagonistic meanings where such preventive measures fail.

The vulnerability of risk regulation to cultural contestation is not a consequence of one or another groups’ hostility to science, of citizens’ “bounded rationality,” or of some inherent drive or appetite on the part of competing groups to impose a sectarian orthodoxy on society.

It is the predictable but manageable outgrowth of the same conditions of political liberty and social pluralism that make liberal democracy distinctively congenial to the advance of scientific knowledge.

By using the hallmark methods of science to protect the science communication environment, we can assure our enjoyment of the unprecedented knowledge and freedom that are the hallmarks of liberal democracy.



Don't be a science miscommunicator's dope (or dodo)

I've blogged about how the NRA uses the expressive "rope-a-dope" tactic to lure gun-control proponents into a style of advocacy that intenstifies cultural antagonism and thus deepens public resistance to engaging sound empirical evidence.

But the same tactic is used--the same trap laid--by enemies of constructive public engagement with decision-relevant science in other areas. Randy Olson's Flock of Dodos is a brilliant, and brilliantly entertaining, demonstration of the dynamic at work in the evolution debate.

The CCP Vaccine Risk Perception and Ad Hoc Risk Communication report warns risk communicators to avoid the "rope-a-dope" trap when engaging propagators of vaccine misinformation:

4. Risk communicators and advocates should be wary of the expressive “rope-a-dope” trap.

Cultural contestation over risks or other facts that admit of scientific inquiry is inherently disruptive of the processes by which ordinary citizens come to know what is known to science (Bolsen & Druckman 2013; Kahan 2013a). When positions become conspicuously identified with membership in identity-defining affinity groups, diverse individuals will not only be exposed disproportionately to information that reflects the position that predominates in their groups. They will also experience psychic pressures that motivate them to use their critical reasoning dispositions to persist in those positions in the face of contrary evidence (Kahan, Peters et al. 2013). For this reason, polarization will be even more intense among members of these groups whose science comprehension capacities are greatest (Kahan 2013b; Kahan, Peters et al. 2012). Because these individuals understandably play a key role in certifying what is known to science within their groups, their divisions will even more deeply entrench other group members’ commitment to the position that predominates among their peers.

Groups intent on promoting cultural polarization can actually use this dynamic to their advantage. By engaging in provocative, culturally partisan and indeed often purely symbolic attacks on positions they disagree with, interest groups can provoke their opponents into denouncing them and their positions in terms that are similarly partisan, recriminatory, and contemptuous. The spectacle of dramatic conflict is what transmits to ordinary citizens—most of whom are largely uninterested in politics and lacking strong partisan sensibilities (Zaller 1992)—that the issue in question is one on which competing positions are badges of group membership and loyalty. That signal benefits the sponsors of group conflict. Indeed, the influence that open conflict exerts on members of the opposing groups will be much stronger than any influence the sponsors of such conflict could have generated by acting alone, not to mention much stronger than the content of the arguments that either side is making.

Vaccine-risk communicators should be wary of this trap, which has been used effectively against advocates of climate science (Pielke 2013) and gun control (Kahan 2013c). Responding to misinformation necessarily elevates the profile of the misinformers. It also creates a deliberative atmosphere in which culturally partisan advocates (some out of innocent exuberance, but others out of a motivation to assimilate vaccine-risk communication into a broader portfolio of publicly arousing issues) will predictably resort to divisive attacks, ones akin, say, to those that inform the “anti-science” trope.

Conspicuous instances of conflict among groups whose members are associated with competing styles and who resort to culturally assaultive idioms are what generates in the minds of ordinary members of the public the impression that disputed positions are aligned with membership in competing groups. It was likely because so many parents of diverse outlooks learned of the HPV vaccine from exchanges like these—as opposed to exchanges with pediatricians or other health experts—that that that vaccine triggered a volume of controversy experienced by no other universal childhood or adolescent vaccine, including the HBV vaccine, which also protects people from a sexually transmitted disease and which is widely included in the schedule of vaccinations required for school enrollment in the vast majority of states (Kahan 2013a).

Steering childhood vaccines clear of the risk of this disorienting form of conflict certainly does not mean that misinformation should routinely be ignored. But it does mean that risk communicators should make a careful assessment of the need to respond, and where there is such a need how to present corrective information in a manner that is free of resonances that convey cultural partisanship.


Bolsen, T., Druckman, J. & Cook, F.L. The Effects of the Politicization of Science on Public Support for Emergent Technologies. Institute for Policy Research Northwestern University Working Paper Series (2013). 

Kahan, D.M. A Risky Science Communication Environment for Vaccines. Science 342, 53-54 (2013a).

Kahan, D.M. Ideology, Motivated Reasoning, and Cognitive Reflection. Judgment and Decision Making 8, 407-424 (2013b).

Kahan, D.M. The NRA’s "Expressive-Rope-a-Dope-Trick". in Cultural Cognition Project Blog (Sept. 3, 2013c).

Kahan, D.M., Peters, E., Dawson, E. & Slovic, P. Motivated Numeracy and Enlightened Self Government. Cultural Cognition Project Working Paper No. 116 (2013)

Kahan, D.M., Peters, E., Wittlin, M., Slovic, P., Ouellette, L., Braman, D. & Mandel, G. The polarizing impact of science literacy and numeracy on perceived climate change risks. Nature Climate Change 2, 732-735 (2012).


Culture, rationality, and the tragedy of the science communications commons (lecture synopsis and slides)

Enjoyed the privilege and pleasure of delivering a lecture at the vibrant,  bustling University of Nottingham last night. The culture that I and the audience members—students and faculty from the university and curious, critical-thinking members of the larger community—share creates an affinity between us that makes us more like one another than either of us is like most of the members of our respective societies. But of course the U.S. and U.K. both enjoy public cultures that enable those who see pursuit of knowledge and exchange of ideas as the best life--a truly peculiar notion in the eyes of the vast majority--to live it. Are we not morally obliged to reciprocate this benefit? 

I wish I had spoken for less time so that I could have engaged my friends in discussion for longer.  But slides here, and a reconstruction of my fuzzy recollection of what I said below.  

0. The science communication problem.  The science communication problem refers to the failure of valid, compelling, and accessible scientific evidence to dispel public conflict over risks and other policy-relevant facts to which that evidence applies. The climate change controversy is the most conspicuous instance of this phenomenon but is not the only one: historically nuclear power and chemical pesticides generated conflicts between expert and public understandings of risk; today disputes of GM foods in Europe and the HPV vaccine in the U.S. feature forms and levels of political controversy over facts that admit of empirical investigation as well. 

Of course, no one should find it surprising that risk regulation and like forms of science-informed policymaking are politically contentious. Facts do not determine what to do; that depends on judgments of value, which naturally, appropriately vary among reasoning people in a free society. 

But values don’t determine facts either.  The answer to the question whether the earth’s temperature has increased in recent decades as a result of human activity turns on empirical evidence the proper understanding of which is the same whether one is an “individualist” or an “egalitarian,” a “liberal” or a “conservative,” a  “Republican” or a “Democrat.”

Accordingly, whatever position one thinks the best evidence supports, one should be puzzled by the science communication problem.  Indeed, one should be puzzled even if one thinks the best available evidence doesn’t clearly support any particular position: there’s no reason why people of diverse values should be unable to recognize that, much less for them to form positions in such circumstances that so strongly correlate with their views about the best way to live. 

So what explains the science communication problem? And what, if anything, can be done about it?

I will describe evidence relating to two hypothesized explanations for the science communication problem, and then advance a set of normative and prescriptive claims based on what I think (for the time being, of course) is the account that the evidence most compellingly supports.

1. 2 hypotheses & some evidence.  The dominant account of the science communication problem among both the academic and the popular commentators (including the many popular commentators who pose as scholarly ones) is the “public irrationality thesis” (PIT).  PIT is related to the often-derided “knowledge deficit” theory—a position I’m not actually sure any serious scholar has ever advanced—but in fact puts more emphasis on the public’s capacity to give proper effect to scientific evidence of risk. Building on Kahneman’s popularization of the “system 1/system 2” conception of dual-process reasoning, PIT attributes public controversy over climate change and other societal risks to the public’s excessive reliance on unconscious, affect-driven heuristics (“system 1”) and its inability to engage in the conscious, effortful, analytic analysis (“system 2”) form that characterizes expert risk analysis.

If PIT proponents were trying to connect their understandeing to the evolving empirical evidence on public risk perceptions, they’d surely be qualifying their incessant, repitious, formulaic espousal of it. Those members of the public who display the greatest degree of “system 2” reasoning ability—are no more likely to hold views consistent with scientific consensus. Indeed, they are even more likely to be culturally and ideologically polarized than members of the public who are most disposed to use “system 1” heuristic forms of reasoning.

A second explanation for the science communication problem is the “cultural cognition thesis” (CCT).  CCT posits that the stake individuals have in their status in affinity groups whose members share basic understandings of the best life can be expected to interact with the various psychological processes by which they make sense of evidence of risk.  Supporting evidence includes studies showing that individuals much more readily perceive scientists to be “experts” worthy of deference on disputed societal risks when those scientists support than when they oppose the position that is predominant in individuals’ cultural group.

This selectivity can be expected to generate diverging perceptions of what expert consensus is on disputed risks.  And, indeed, empirical evidence confirms this prediction.  No cultural group believes that the position that is dominant in its group is contrary to scientific consensus—and across the run of disputed societal risks, all of the groups can be shown to be poorly informed on the state of expert opinion.

The magnification of polarization associated with the disposition to engage in “system 2” forms of information processing also fits CCT.  Individuals who are adept at engaging empirical evidence have a resource that those who must rely more on “system 1” substitutes lack for ferreting out evidence that supports their group’s position and rationalizing away the evidence that doesn’t.

2. The tragedy of the science communications commons. PIT, then, has matters essentially upside down. The source of the science communication problem is not too little rationality on the part of the public but rather too much.  The behavior of an ordinary individual as a consumer, a voter, or an advocate, etc., can have no material impact on the level of risk that person or anyone else faces from climate change. But if he or she forms a position on that issue that is out of keeping with the one that predominates in that person's group, he or she faces a considerable risk of estrangement from communities vital to his or her psychic and material well-being.  Under these conditions, a rational actor can be expected to attend to information in a manner that is geared more reliably to forming group-congruent than science-congruent risk perceptions.  And those who are highest in critical reasoning dispositions will do an even better job than those whose “bounded rationality” leave them unable to recognize the evidence that supports their groups’ position or to resist the evidence that  undermines it.

But as individually rational as this form of information processing is, it is collectively irrational for everyone to engage in it simultaneously. For in that case, the members of a self-governing society are less likely to converge or converge as quickly as they otherwise would on the best available evidence.

Yet even that won’t make it any more rational for an individual to attend to information in a manner reliably geared to forming science- as opposed to group-congruent beliefs—because, again, nothing he or she does based on a “correct” understanding will make any difference anyway.

This misalignment of individual and collective interests in the formation of risk perceptions consistent with the best available evidence is the tragedy of the science communications commons.

3. A polluted science communication environment. The signature attributes of the science communication problem—the correlation between perceptions of risk and group-defining values, and the magnification of this effect by greater reasoning proficiency—is pathological.  It is not only harmful, but unusual.  The number of societal risks that reflect this pattern relative to the number that do not is tiny.

In the cases in which diverse members of the public converge on the best available evidence, the reason is not that they genuinely comprehend that evidence. Individuals must, not only to live well but simply to live, accept as known by science much more than they could ever make sense of, much less verify, on their own. 

Ordinary individuals manage to align themselves appropriately with decision-relevant science essential to their individual and collective well-being not by becoming experts in substantive areas of knowledge but by becoming experts in identifying who knows what about what.  Nullius in verba—or “take no one’s word for it,” the motto of the Royal Society—is charming but silly if taken literally.  What’s essential is to take the word only of those whose knowledge has been attained by the methods of ascertaining knowledge distinctive of science.

The remarkable ability that ordinary members of the public—ones of diverse reasoning dispositions as well as diverse values—to reliably identify who knows what about what breaks down, however, when positions on issues become entangled in meanings that transform them into symbols of group identity and loyalty.  At that point, the stake individuals have in forming group-congruent beliefs will dominate the stake they have in forming science-congruent ones.

Such meanings, then, are a kind of pollution in the science communication environment. They disable the normally reliable faculties that individuals use to ascertain what is known to science.

4. “. . . a new political science . . .” (a) Risks are not born with antagonistic cultural meanings but rather acquire them through one or another set of events that might well have turned out otherwise.

It wasn’t inevitable, for example, that the HPV vaccine would acquire the divisive association with contested norms on gender, sexuality, and parental autonomy that polarized opposing groups’ perceptions of its risks and benefits in the U.S. The HBV vaccine also confers immunity from a sexually transmitted disease that causes cancer (hepatitis-b), and the CDC’s recommendation to add it to the schedule of vaccinations required as a condition of middle school enrollment generated no meaningful controversy among culturally diverse citizens—over 90% of whose children received the shot every year during which the states were embroiled in controversy over making the HPV shot mandatory.

The antagonistic cultural meanings that fuel political controversy over GM foods in Europe aren’t inevitable either.  They are completely absent in the U.S.

(b) The same methods that scholars of public risk perception use to make sense of these differences, moreover, can be used to forecast the conditions that make one or another emerging technology—such as synthetic biology or nanotechnology—vulnerable to becoming suffused with such meanings. Action can then be taken to steer these technologies down a safer path—not for the purpose of making members of the public believe they are or aren’t genuinely hazardous, but rather for the purpose of assuring that members of the public will reliably recognize the best available evidence on exactly that.

Indeed,  the danger of cultural polarization associated with the path the HPV vaccine traveled in being introduced to the public was forecast with such methods, which corroborated the warnings of numerous health professionals and others.

This evidence wasn’t rejected; it simply wasn’t considered. There’s was no mechanism in any part of the drug-regulatory approval process for anyone to present, or any institution to act, on evidence on the hazards associated with fast-track approval of a girls-only STD vaccine combined with a high-profile nationwide campaign in state legislatures to make the vaccine mandatory.

(c)  Without systematic procedures to acquire and intelligently use scientific knowledge to protect the science communication environment, its contamination is inevitable.

The inevitable danger of such conflicts is built into the constitution of the Liberal Republic of Science. The same institutions and culture of political freedom that fuel the engine of competitive conjecture and refutation that drives science assure—mandate—that there by no single institution endowed with the authority to certify what is known to science. But the immensity and complexity of what is known cannot certify or announce itself; the idea that it can is the sentimental, sociologically and epistemologically naïve variant of nullius in verba.

In the Open Society there will be a plurality of certifiers—in the form of communities of free individuals associating with others with whom they have converged in the exercise of their reason on a shared understanding of the best way to live. 

This dynamic, unregulated, pluralistic system of certification of what is known to science works in the vast run of cases!

Yet it is inevitable—statistically!--that it sometimes won’t: the sheer enormity of things that science can discern in a free society & the non-zero probability that any one of those can become entangled in antagonistic cultural meanings mean that risk regulation will remain a permanent site of illiberal forms of status competition among the plurality of cultural groups in which free, reasoning individuals form their understanding of what is known to science. This is Popper’s revenge . . . .

It is foolish (an embarrassing display of shallow thinking combined with indulgence of tribal chauvinism) to blame “profit-mongering corporations” or “political extremists” for disasters like the one that occurred with the introduction of the HPV vaccine in the U.S. ”  Until we—the citizens of the Liberal Republic of Science—use our reason and exercise our will to create a common culture of evidence-based science communication dedicated to protecting the science communication environment, we are destined to suffer the reason-effacing, welfare-enervating, freedom-annihilating spectacle of cultural conflict over risk.

(d) Writing at the birth of liberal democracy, Tocqueville famously remarked the need for “a new political science for a world itself quite new.”

Today we need a new political science—a science of science communication –dedicated to protecting the process by which plural communities of free and reasoning individuals certify to themselves what is known by science.

We must use our reason to protect the historic condition of freedom and the unprecedented immensity of collective knowledge that are the reciprocal defining features of the Liberal Republic of Science. 


"Motivated Numeracy": What's the Point? (lecture synopsis, slides)

Gave lecture /workshop today at Cambridge. It was advertised as being a session on the CCP working paper, “Motivated Numeracy and Enlightened Self-Government.”  It was—but I added some context/motivation.  Outline of what I remember saying below & slides here.  Lots of great questions & comments after—on issues from the influence of cultural cognition on scientists to the relative potential impact of fear & curiosity in fortifying critical reasoning dispositions!

I. What’s the point? The “Motivated Numeracy” study is the latest (more or less) installment in a series intended to make sense of and maybe help solve the science communication problem. The “science communication problem” refers to the failure of valid, compelling, and widely accessible scientific evidence to dispel public controversy over risks and other policy-relevant facts. Climate change is a salient instance of the problem but is not the only one. The conflict between public and expert views on the safety of nuclear power once attracted nearly as much attention. There are other contemporary instances of the science communication problem, too, including the controversy over mandatory HPV vaccination in the US and GM foods in Europe (but actually not in the US).

II.  Two theories. What accounts for the science communication problem?  One explanation, the “public irrationality thesis,” attributes public controversy over climate change and other societal risks to the public’s limited capacity to comprehend science. The problem is only part one of a “knowledge deficit”; more important is a deficit in critical reasoning. Members of the public rely excessively on largely unconscious, heuristic-driven forms of information processing and thus overestimate more emotionally compelling dangers—such as terrorism—relative to less evocative ones like climate change, which the conscious, analytic modes of risk analysis used by experts show are even more consequential.  Informed by Kahneman’s “system 1/system2” conception of dual process reasoning, PIT is more or less the dominant account in popular and academic commentary.

Another account of the science communication problem is the “cultural cognition thesis.” Cultural cognition involves the tendency of individuals to conform their perceptions of risk and other policy-relevant facts to the positions that are dominant in the affinity groups that play a central role in organizing their day-to-day lives.  As a species of motivated reasoning, CCT is distinguished by its use of Mary Douglas’s “cultural worldview” framework to specify the core commitments of the affinity groups that shape information processing.  CCT is distinguished from  other conceptions of the “cultural theory of risk” by its attempt to root the influence that group commitments of this sort play in shaping perceptions of risk in cognitive mechanisms that admit of empirical investigation by the methods featured in social psychology and related disciplines.

III.   Three studies. Motivated Numeracy describes the third in a series of studies dedicated to investigating the relationship between PIT and CCT.  The first study, an observational one that examined the climate-change risk perceptions of a large nationally representative sample, made two findings at odds with PIT. 

The first finding had to do with the impact of science comprehension on the perceived risk of climate change. If, as PIT asserts, the reason that the average member of the public is less concerned with climate change risks than he or she should be is that he or she lacks the capacity to make sense of scientific evidence, than one would expect people to become more concerned about climate change as their science literacy and quantitative reasoning abilities increase.  But this isn’t so: the study found that the impact of these attributes on climate change risk was close to zero for the sample as a whole.

The second finding contrary to PIT had to do with the relationship between science comprehension and cultural cognition.  PIT views cultural cognition as just another heuristic substitute for the capacity to understand and give proper effect to scientific evidence of risk: those who can are reliably guided by the best available evidence; those who can’t must with their gut, which is filled with crap like “what do people like me believe?”  If this position is correct, one would expect the risk perceptions of culturally diverse individuals to be progressively less correlated with their groups and more correlated across groups as their science comprehension capacity increases.

But not so.  On the contrary, cultural polarization, the first study found, increases as science comprehension does.

Why? The CCT explanation is that individuals are using their knowledge of and capacity to reason about scientific evidence to form and persist in beliefs that reflect their group identities.

The second study used experimental methods to test this hypothesis.  The study found, consistent with CCT, that individuals who display the strongest disposition for cognitive reflection—a habit of mind associated with conscious, effortful system 2 reasoning—are more likely to discern the ideological implications of conceptually complicated information and selectively credit or reject it depending on its congeniality to their cultural outlooks.

The third and final study—the one the results of which are reported in “Motivated Numeracy”—likewise used an experimental design to assess whether individuals can be expected to use their critical reasoning dispositions in a manner that promotes identity-congruent rather than truth-congruent beliefs.  The study compared the interaction of right-left ideology (an alternative way to measure the group affinities that generate cultural cognition) with numeracy, a quantitative reasoning capacity associated with “system 2” information processing. 

Subjects were instructed to examine a problem understood to be a predictor of their vulnerability to a defective heuristic alternative to the assessment of covariance.  The problem involved assessing whether the results of an experiment supported or negated a hypothesis.  For subjects in the “control group,” this problem was styled as one involving the effectiveness of a new skin-rash treatment.  As expected, only the most highly numerate subjects were likely to correctly interpret the experimental data.

Another version of the problem was styled as an experiment involving the effectiveness of a ban on carrying concealed weapons.  In this condition, high-numerate subjects again did much better than low-numerate ones but only when the data properly construed generated an ideologically congenial result. When the data, properly construed, supported an ideological noncongenial result, high numerate subjects latched onto the incorrect but ideologically satisfying heuristic alternative to the logical analysis required to solve the problem correctly.

Because high-numeracy subjects used their quantitative reasoning powers selectively to credit evidence that low-numeracy subjects could not reliably interpret, high-numeracy subjects ended up more likely on average to disagree than low-numeracy ones.  The impact of science comprehension in magnifying cultural polarization on climate change is consistent with exactly this pattern of ideologically opportunistic critical reasoning.

IV. One synthesis.  The studies investigating the interaction of PIT and CCT support (provisionally, as always!) a cluster of interrelated descriptive, normative, and prescriptive conclusions. 

 A. The tragedy of the science communication commons. The science communication problem is a result not of too little rationality but rather too much.  Because the beliefs and actions of any ordinary individual member of the public can’t affect climate change, neither she nor anyone she cares about will be put at risk if she makes a mistake in interpreting the best available evidence.  But if such a person forms a position that is out of keeping with the dominant one in her affinity group, the consequences—in estrangement from those she depends on for support—can be extremely detrimental.  It thus is individually rational for individuals to attend to information on societal risks that more reliably connects their beliefs to those shared by others with their defining outlooks than to the best available evidence.  The more proficient they are in reasoning about scientific evidence, moreover, the more successful they’ll be in forming and persisting in such beliefs.

Such behavior, however, is collectively irrational. If all individuals pursue it simultaneously, they will not converge or converge as quickly as they should on valid evidence essential to their welfare.  Yet this predictable consequence will not change the psychic incentive that any individual faces to form group- rather than truth-convergent beliefs.

The science communication problem thus involves a distinctive form of collective action problem—a tragedy of the science communications commons.

B. Pathological meanings. The signature attributes of the science communication problem—cultural polarization magnified by science comprehension—are not normal. The number of risk perceptions and like beliefs that display this pattern relative to the number that do not is tiny. On issues from fluoridation of water to the safety of medical x-rays, the most science comprehending individuals do converge, pulling along those who share their cultural outlooks.  This process of knowledge transmission breaks down only when positions on disputed issues become symbols of membership in and loyalty to competing groups—at which point the stake ordinary individuals will have in forming group-convergent beliefs will systematically dominate the stake they have in forming truth-congruent ones. 

This sort of entanglement of risk perceptions and culturally antagonistic meanings is a pathology—both in the sense of being harmful and in the sense of being unusual or opposed to the normal, healthy functioning of collective belief formation.

C. “Scicomm environment protection” as a public good.  The health of a democratic society depends on the quality of the science communication environment just as the health of its members depends on the quality of the natural one.  Antagonistic cultural meanings are a form of pollution in the science communication environment that disables the exercise of the rational faculties that ordinary citizens normally and reliably use to discern what’s known to science. Protecting the science communication environment from this toxin is a public good essential to enlightened self-government. 

By  using reason, we can protect reason from the distinctive threats that the science communication problem comprises.


Cross-cultural cultural cognition road trip

Here's my schedule for next week and a half -- or at least parts of it.  


Stop by if in the neighorhood -- otherwise I'll send postcard reports now & again!

(Actually, I'm surprised that I'm giving the same talk at Cardiff & Nottingham--but I doubt that I really will!)


Science journalists: Ask not what the science of science communication can do for you . . . 

A reflective correspondent & friend wrote to me to ask what I made of the relative inattention of science journalists to the empirical study of science communication--& what might be done to remedy this.  She had many great ideas for how to make such work more familiar and accessible to them.  I had a somewhat different, but I think complementary reaction:

I think it is unsurprising how infrequently empirical research is featured in social media and similar fora in which science journalists exchange ideas.

The explanation, moreover, isn't merely that how to communicate to curious members of the public is only 1 of the n things that science of science communication studies. It's that those who are engaged in scientifically studying science communication -- including the sorts science journalists do -- aren't trying to answer the questions that journalists most often are, and should be, asking.  

The journalists' questions relate to their own craft norms -- the professional understandings that they absorb and generate and transmit and that guide and animate them.  They argue about various ones of them all the time, in many cases persistently (or at least intermittently; they have jobs—very interesting ones!) over long periods of time.

That means that they have questions that in the judgment of those endowed with the requisite, experience-informed professional judgment admit of more than one plausible (but not, the debate presupposes, more than one correct or best) answer.  

Under those circumstances, arguments will be interminable and make no progress. Evidence is needed -- not as a substitute for the exercise of professional judgment but as raw material for it to operate on.  

Well, very very few (maybe zero) scholars are using empirical methods to answer questions of consequence to the quality and evolution of science journalism's' craft norms.  

Most “science of #scicomm” scholars, of course, aren't studying science journalism at all.  

Others actually are-- but to answer questions that are parts of the scholarly conversations those researchers are part of.  They have converged on (or joined) collective inquiries into how one or another general mechanism—cognitive, political, or both—operate to shape the path of scientific information through the media and to the public.  Their research (much of which is excellent!) is, nearly always, trying to answer questions that admit of more than one plausible (but not more than one correct or best) answer about those processes—not about how science journalists can be excellent science journalists.

Maybe sometimes these scholars mistakenly think that what they are studying when they examine these more general dynamics of communication supplies the "answers" to the questions science journalists pose about their own craft norms. Other times they present their work this way knowing full well that it is a mistake (it's a very disturbing spectacle when they do).

In either case, science journalists react negatively -- "that's ridiculous" or (in a refrain that becomes a chorus after an event like NAS “science of #scicomm” colloquia) "that's completely irrelevant to what we do; I've not learned a thing!"  ...

Well, the problem actually isn't in the researchers here; it's in the science journalists!

The mistake is in part for them to think that "everything is about them": the science of science communication isn't one thing—it’s 7 (± 2).  

But even more fundamentally, it is a mistake for the science journalists to think that anyone besides them can be expected to create the scientific insight that is relevant to their craft!

No one else knows (or likely genuinely cares: nonjounralists don't even know enough to care) what the empirical questions of consequence to science journalism's craft norms are. No one else can reliably recognize the form of evidence that helps professional conversation about those questions to advance; only those with the sense of the professional science journalists can.

This isn't to say that individual journalists must start designing studies and collecting data.  Rather it is to say that they must exercise control over research using empirical methods so that it in fact is designed to address questions of consequence to them and uses designs that can support inferences relevant to the sorts of questions experienced science journalists recognize as admitting of more than one plausible (but not more than one correct or best) answer.  

Science journalists will often observe, correctly, that “science of #scicomm” scholars' work on general mechanisms are generating insights of indisputable relevance to their craft.  But the journalists--not the scholars--will know when that's so.  

In that situation, moreover, science journalists will be filled with hypotheses--ones that are concrete and relevant to those who share their situation sense—about how those mechanisms might interact with their professional craft norms.

Even if they did not themselves create the studies, they will recognize when one designed to test such a hypothesis is genuinely capable of supporting inferences on the basis of which they can will know more than they otherwise would have

They are the ones, then, who must direct the empirical enterprise that is the science of science communication for science journalists.


There are an infinite number of ways -- but none of them consists in passively consuming journal articles.

Here as in the other practical domains in which a science of science communication is needed, the answer of the thoughtful and honest scholar who actually wants to help when asked (over & over) by communicators to "so what should we do" is, "You tell me -- and I will help by measuring what you confirm for me is the right thing!"


Want to know what empirically *informed* vaccine risk communication looks like?

Drawing on material from the CCP Vaccine Risk and Ad Hoc Risk Communication study, the last few posts reported experimental results on the potentially deleterious effects of empirically uniformed risk communication.

By “empirically uninformed risk communication,” I mean to refer to information that accurately conveys the safety and efficacy of vaccines but that embeds that information in mischaracterizations of the extent, nature and consequences of public hostility to universal childhood immunization.  Ad hoc risk communication of this sort—which abounds in the media and on the internet—itself can produce misunderstandings that undermine the motivation to cooperate with universal immunization programs and that drag childhood vaccinations into the reason-effacing maelstrom of cultural conflict (Kahan 2013).

What’s more, this style of risk communication distracts those who want to promote public understanding of vaccine safety from the need to perfect empirically informed strategies for achieving this critical goal.

Such research is well underway.

As discussed in the Report, it consists not in general public opinion surveying: opinion polls lack sufficient discernment to identify the sources and mechanisms of genuine vaccine hesitancy in the public, and are not a reliable or valid measure of vaccine behavior by parents.

The most valuable research now being conducted on vaccine hesitancy uses focused and fine-grained methods tied to actual behavior.

Dr. Douglas Opel and his collaborators (2011a, 2011b, 2013), e.g., have devised—and are refining—an attitudinal screening instrument that can be used to predict parents’ willingness to obtain timely vaccinations for their children.  Such a screening device would be comparable to ones used in diverse fields from credit assessment (e.g., Klinger, Khwaja & Lamonte 2013) to organizational staffing (e.g., Ones et al. 2007), not to mention to ones used to predict or diagnose disease vulnerability (e.g., Wilkins et al. 2013).

If perfected, such an instrument could be used by physicians to identify genuinely vaccine-hesitant parents, by public health administrators to detect local pockets of under-vaccination that pose a genuine public health threat, and by researchers to develop genuinely effective risk communication materials (Sadaf et al. 2013; Opel et al. 2012)—ones that can convey factually accurate information to the right people and avoid all the hazards associated with blunderbuss, empirically uninformed ad hoc risk communication.

Of course, the public health risks posed by local enclaves of under-vaccination, as well as by misinformers who sow unfounded anxiety in these and other communities, are ones that merit response right now.

The public health establishment doesn’t have as much evidence as it needs to address these dangers as effectively as it could.

But as such evidence is being developed by valid empirical research, those who favor universal childhood immunization should make intelligent use of the currently best available evidence to promote constructive and open-minded public engagement with valid information on vaccine risks and benefits.

If you want an example, I urge you to read this excellent essay from Moms Who Vax:

It may surprise you to know that the anti-vaccine movement has long claimed to speak for parents in this country when it comes to vaccines. And it is because they are so vocal and we are so, well, busy living our lives, that legislators, government officials, and even some public health organizations think that anti-vaccine activists who believe the MMR causes autism and that the decline of vaccine-preventable disease is due to "better hygiene" represent parents as a whole, when it comes to immunization in this country.

The vast--vast--majority of us choose to vaccinate our children for two reasons: one, we don't want our children to suffer from a preventable disease, possibly become seriously ill, or even die; and two, we don't want any of those things to happen to our neighbors either. Here's the problem: we don't talk about it. I suspect this is because we consider it commonsense. One mother on this blog wrote a post titled: "There's an Anti-Vaccine Movement?" because it had never occurred to her before she had children that people would willingly forgo something that has nearly eliminated one of the most dreaded diseases in human history (polio) and saved the lives of countless children and adults from other diseases that, if not kept in check by widespread immunization, cause unimaginable amounts of suffering.

We never thought we'd have to advocate for something that saves lives, especially the lives of children.

But here we are, and our complacency and our silence has allowed a fringe minority to sit at the table of public health in our place. And there are now consequences for our silence.

If I sound a little more passionate than usual, it's because I'm angry. We must rise up as a group and take back the conversation. … Right now, there are legislators in Oregon who believe that millions of parents do not believe in vaccination.... Let's prove them wrong. … Let's do this--let's go letter for letter, and beyond. Let's make sure the people who make our immunization law know that we are here, that we care, that we are the 95%.

In addition to being much more eloquent and inspiring than the boilerplate “growing crisis of confidence” and “creeping anti-science” tropes that dominate ad hoc risk communication, this essay brilliantly exploits dynamics that a reflective communicator would surmise are important based on existing, evidence-based understandings of science communication:

  • Because individuals (quite sensibly!) form their assessments of risk by observing how others who are like situated are responding (Kasperson et al. 1988), the (clear, unassailablefact that the “vast majority” of U.S. parents arrange for their children to receive all recommended immunizations is itself an important and effective piece of evidence to communicate to parents—many of whom are likely to become fearful if bombarded by thoughtless repetition of the false message that an “epidemic of fear” has led to an erosion in immunization rates. 
  • Similarly, people tend to contribute voluntarily to collective goods when they perceive that others are doing so but to refrain when they think that others are shirking or free-riding (Bowles & Gintis 2013).  So again, the message here—“we are the 95%” who contribute—is spot on.  It reinforces reciprocal motivations to contribute to the collective good of herd immunity (Hershey et al. 1994) rather than undermines them, as empirically uninformed risk communicators do by proclaiming—falsely—that a “large and growing number” of “otherwise mainstream parents” are refusing to vaccinate their children.   
  • The communication manifests the willingness of the vast majority who are contributing to the public good of herd immunity to contribute to another: condemnation of the few who are free-riding. Experimental behavioral economics shows that individuals are most likely to converge on and stick to a high-cooperation equilibrium in a collective action setting when they can observe that other individuals are moved voluntarily to accept the burden of informally punishing (e.g., by shaming) the relatively few selfish actors who free-ride.  In contrast, demands for increased, centrally administered formal punishments can vitiate reciprocal motivations by convey an expectation that the disposition to voluntarily comply is lower than it actually is (Kahan 2004)—another of the many sources of scientific insight that empirically uninformed risk communicators ignore
  • Finally, this essay is inspiringly inclusive.  It doesn’t use the cheap trick of ramping up one cultural group’s indignation by attributing socially undesirable behavior to a competing one. Characteristic of communications that—again, falsely—attribute vaccine hesitancy to one or another recognizable cultural or political group, this style of advocacy is what threatens to envelop childhood vaccines in exactly the same forms of persistent cultural conflict that inhibit public recognition of the best available evidence on myriad issues—from climate change to nuclear power to the HPV vaccine.

We need to acquire more valid empirical evidence on how to communicate vaccine risks and benefits.

But we also need to act in an informed way in the meantime.

Another of the many defects of empirically uninformed vaccine risk communication is that it diverts attention away from the most instructive and inspiring examples of how public-spirited citizens and scientists are pursuing these objectives.


Bowles, S. & Gintis, H. A cooperative species : Human reciprocity and its evolution (Princeton University Press, Princeton, 2013).

Kahan, D.M. The Logic of Reciprocity. in Moral Sentiments and Material Interests: The Foundation of Cooperation in Economic Life (ed. H. Gintis, S. Bowler & E. Fehr) 339-378 (MIT Univ. Press, Cambridge, MA, 2004).

Kahan, D.M. A risky science communication environment for vaccines. Science 342, 53-54 (2013).

Kasperson, R.E., et al. The Social Amplification of Risk: A Conceptual Framework. Risk Analysis 8, 177-187 (1988).

Klinger, B., Khwaja, A. & LaMonte, J. Improving credit risk analysis with psychometrics in Peru. (Inter-American Development Bank, 2013).

Ones, D.S., Dilchert, S., Viswesvaran, C. & Judge, T.A. In support of personality assessment in organizational settings. Personnel Psychology 60, 995-1027 (2007).

Opel, D.J., Mangione-Smith, R., Taylor, J.A., Korfiatis, C., Wiese, C., Catz, S. & Martin, D.P. Development of a survey to identify vaccine-hesitant parents: The parent attitudes about childhood vaccines survey. Human Vaccines 7, 419-425 (2011a).

Opel, D.J., Robinson, J.D., Heritage, J., Korfiatis, C., Taylor, J.A. & Mangione-Smith, R. Characterizing providers’ immunization communication practices during health supervision visits with vaccine-hesitant parents: A pilot study. Vaccine 30, 1269-1275 (2012).

Opel, D.J., Taylor, J.A., Mangione-Smith, R., Solomon, C., Zhao, C., Catz, S. & Martin, D. Validity and reliability of a survey to identify vaccine-hesitant parents. Vaccine 29, 6598-6605 (2011b).

Opel, D.J., Taylor, J.A., Zhou, C., Catz, S., Myaing, M. & Mangione-Smith, R. The relationship between parent attitudes about childhood vaccines survey scores and future child immunization status: A validation study. JAMA pediatrics 167, 1065-1071 (2013)

Sadaf, A., Richards, J.L., Glanz, J., Salmon, D.A. & Omer, S.B. A Systematic Review of Interventions for Reducing Parental Vaccine Refusal and Vaccine Hesitancy. Vaccine 31, 4293-4304 (2013)

Wilkins, C.H., Roe, C.M., Morris, J.C. & Galvin, J.E. Mild physical impairment predicts future diagnosis of dementia of the Alzheimer’s type. Journal of the American Geriatrics Society 61, 1055-1059 (2013).


The culturally polarizing effect of the "anti-science trope" on vaccine risk perceptions 

The “ ‘anti-science’ trope” refers to a common theme in ad hoc risk communication that links concern about vaccine risks to disbelief in evolution and climate skepticism, all of which are cited as instances of a creeping hostility to science in the U.S. general public or at least some component of it.

In the last post, I presented evidence, collected as part of the CCP Vaccine Risk Perception study, that showed that the trope has no meaningful connection to fact. 

Those who accept and reject human evolution, those who believe in and those who are skeptical about climate change, all overwhelmingly agree that vaccine risks are low and vaccine benefits high.

The idea that either climate change skepticism or disbelief in evolution denotes hostility to science or lack of comprehension of science is false, too. That’s something that a large number of social science studies show.  The CCP Vaccine Risk study doesn’t add anything to that body of evidence.

But the CCP Vaccine Risk study did examine how differences in science comprehension and religiosity, which interact in an important way in disputes over climate change and evolution, don’t have any meaningful impact on perceptions of vaccine risk perceptions.

In addition to examining whether there was any factual substance to the anti-science trope, the CCP Vaccine Risk Perception study also investigated what the impact of the trope is—or at least could be if it were propagated widely enough—on public opinion.

For that purpose, the study used experimental methods. The experiment had three key elements.

First was a measurement of subjects’ cultural predispositions toward societal risks.

 I’ve actually described the strategy used to do so in several earlier posts.  But basically, the experiment used an “interpretive community” strategy, in which unobserved or latent group predispositions are extracted from subjects perceptions of a host of societal risks that are known to divide people with diverse cultural and political outlooks. This approach, as I’ve explained, furnishes the “highest resolution” for measuring the influence group predispositions might be having on perceptions of a risk on which there is reason to believe the impact might be small.


That analysis identified two cross-cutting or orthogonal dimensions along which risk predispositions could be measured.  I labeled them the “public safety” and “social deviancy” dimensions, based on their respective indicators (various environmental risks, guns, second-hand smoke in the former case; legalization of marijuana and prostitution and teaching of high school sex ed in the latter). 

 Subjects in the diverse 2,300-person sample of U.S. adults could thus be assigned to one of four “interpretive communities” (ICs) based on their score relative to the mean of both of these two “risk perception dimensions”: IC-α (“high public-safety” concern, “low social-deviancy”);  IC-β (“high public-safety,” “high social-deviancy); IC-γ (“low public-safety,” “low public-safety”); and IC-δ (“low public-safety,” “high social-deviancy”).  The intensity of the study subjects' commitment to one or the other of these groups can be measured by their scores on the public-safety and societal-deviancy risk-perception scales.

The second element was exposure of the subjects to examples of “ad hoc risk communication.”

The subjects were assigned to experimental conditions or groups, each of which read a different communication patterned on information in the media or internet.

One of these communications used the “anti-science trope.” Patterned on real-world communications (including ones reproduced in the Appendix to the Report), it was in the form of an op-ed that described disbelief in evolution, climate skepticism, and the belief that vaccines cause autism as progressive manifestations of a mutating “anti-science virus.” As is so for most real-world communications embodying the anti-science trope, the experiment communication displayed an unmistakably partisan orientation and conveyed contempt for members of the public who are skeptical of climate change and disbelieve evolution.

The third element was measurement of the subjects’ perceptions of vaccine risks and benefits.

The study used a large battery of risk and benefit items, which were combined into a highly reliable scale, “PUBLIC_HEALTH” (Cronbach’s α = 0.94), scores of which were transformed into z-scores (i.e., normalized so that increments reflected standard deviations from the mean) and coded so that lower ones denoted relatively negative assessments of vaccines and higher scores relatively positive ones.

In the experiment, then, the risk perceptions of subjects exposed to different forms of “ad hoc risk communication” were compared to the perceptions of survey participants, who were assigned to read a news story unrelated to vaccines and whose members served as the “control” group.

The results . . . .

As previewed in an earlier blog post, the study found that among members of the control group there was no practically meaningful relationship between  vaccine risk perceptions and the cultural risk predispositions measured by the “public safety” and “social deviance” IC dimensions.  IC-αs (“high public-safety,” “low social-deviancy”) scored highest on PUBLIC_HEALTH and IC- δs the lowest.  But the difference between them was trivially small—less than one-third of one standard deviation of the mean score.

As a measure of the practical difference in these scores, the predicted probability of agreeing that the “benefits of obtaining generally recommended childhood vaccinations outweigh the health risks” was estimated to be 84% (± 3%, LC = 0.95) for a typical IC‑α and 74% ( ± 4%) for a typical IC‑δ.

This was consistent with the findings of the Vaccine Risk Perception study's survey component generally, which found that there is broad-based consensus, even among groups that are bitterly divided on issues like climate change and evolution, that vaccine benefits are high and their risks low.  As of today, at least, vaccine risks are not culturally polarizing.

But that could change, the experiment results suggested.

This very modest difference in the perceptions of subjects displaying the IC-α  and IC-δ risk disposition widened significantly among their counterparts in the “anti-science trope” condition. Exposure to the “anti-science” op-ed also drove a wedge between subjects displaying the IC-β (“high public-safety,” “high social-deviancy) and IC-γ (“low public-safety,” “low social-deviancy”) dispositions, groups whose scores on the PUBLIC_HEALTH scale were indistinguishable in the control.

The practical significance of the difference can be illustrated by examining the impact of the experiment on the predicted probability of agreement with the item measuring “confidence in the judgment of the American Academy of Pediatrics that vaccines are a ‘ safe and effective way to prevent serious disease.’ ” Subjects responded to this item immediately after reading a statement issued by the AAP on vaccine testing and safety. The predicted probability that a subject with a typical IC-δ disposition would indicate a positive level of confidence dropped from 73% (± 4%, LC = 0.95) in the control to 64% (± 7%, LC = 0.95) in “anti-science”; the gap between the predicted probability of a positive assessment by a typical IC-δ and a typical IC-α grew 14% (± 9%) in the two conditions. The gap between the typical IC-β and both the typical IC-α (7%; ± 7%, LC = 0.95) and typical IC-δ (6%; ± 6%, LC = 0.95) grew, too, but by a more modest level. As one would expect, similar divisions characterized responses to other items in the PUBLIC_HEALTH scale.

There was no similar decrease in the predicted probability that a typical IC-δ would express a positive level of confidence in the other experiment conditions, one of which which featured a composite news story proclaiming an impending public health crisis from “declining vaccine rates,” and another of which a communication patterned on a typical CDC press release that conveyed accurate information on the high and steady level of vaccine rates in the U.S. in the last decade.  But as discussed in a previous post, subjects in the “crisis” condition, not surprisingly, grossly overestimated the degree of parental resistance to universal immunization—an effect that could negatively affect reciprocal motivations to contribute to the public good of herd immunity.

It is important to realize that the polarizing impact of the “Anti-science” op-ed resulted both from the positive effect it had on the vaccination attitudes of IC-α subjects and the negative effect it had on IC-δ ones. The overall effect of the “Anti-science” treatment was negligible.

The practical importance of the result, then, turns on the significance attached to the intensified levels of disagreement among subjects of diverse outlooks.

Previous CCP studies, including one involving controversy over the HPV vaccine, suggest that the status of a putative risk source as a symbol or focus of cultural contestation is what disrupts the social processes that ordinarily result in public convergence on the best available evidence relating to societal and health risks.

If this is correct, then any influence that intensifies differences among such groups should be viewed with great concern.

The "anti-science trope," in sum, is not just contrary to fact.  It is contrary to the tremendous stake that the public has in keeping its vaccine science communication environment free of reason-effacing forms of pollution.


How are climate skepticism, disbelief in evolution & vaccine hesitancy related?

The dominant theme of ad hoc risk vaccine risk communication warns of a “growing wave of public resentment and fear” that has induced a “large and growing number” of “otherwise mainstream parents” to refuse to vaccinate their children.

As discussed in the last post, this trope is not based on fact: there hasn't been an erosion in immunization rates”; on the contrary, coverage for all recommended childhood vaccines has held steady at 90% (the HHS "healthy person" target) or above for over a decade.

And while there's zero evidence of a " “growing crisis of public confidence in vaccines at present, emphatic assertions that there is one can be shown to induce misunderstandings and confusion inimical to the willingness of people to make voluntary contributions to public goods--like the herd immunity associated with universal immunization.

A secondary theme of ad hoc risk communication is the "anti-science" trope.  This claim links "growing" concern over vaccine safety to disbelief in evolution and skepticism toward climate change, all of which are depicted as evidence of a creeping hostility to science in the general public.

The CCP Vaccine Risk Perception study found this assertion, too, to be both contrary to fact and antithetical to maintaining the existing, broad-based public consensus in favor of universal immunization.

Below is a section of the Report that presents survey evidence on the relationship between vaccine risk perceptions, on the one hand, and climate change skepticism, disbelief in evolution, and science comprehension generally, on the other.  Tomorrow I'll post material relating to the Study's experimental component, which illustrates the potential of the "anti-science trope" to generate cultural conflict over vaccines.

A. Some benchmarks: evolution and climate change, science comprehension and religiosity.  

As emphasized, the aim of the survey component of the study was to evaluate the nature of the general public’s perception of childhood vaccine risks. Is there a shared or dominant affective orientation toward vaccine safety in the U.S. public? Or do childhood vaccines provoke mixed and opposing reactions—and if so, among whom?

Meaningful answers to these questions require an intelligible reference point with which to compare the survey responses. Dispute over universal vaccination laws—provisions that make immunization a condition of school enrollment, subject to medical or religious and in some states moral-objection “exemptions”—are frequently likened to conflicts over acceptance of mainstream science, including the teaching of evolution in public schools and the adoption of policies to mitigate the environmental impact of climate change. Associated with religious, cultural, and political divisions, the intensity and character of these conflicts can be used to help assess the intensity and character of any divisions of opinion observed on childhood vaccine risks.

The study measured study participants’ beliefs about both evolution and global warming. On evolution, subjects responded to an item from the National Science Foundation (2012) “Science Indicators” battery, which is conventionally used to measure science literacy. That item instructs respondents to respond to the statement “Human beings, as we know them today, developed from earlier species of animals.” In line with many public opinion polls (e.g., Newport 2012), 56% of the survey respondents classified this statement as “true,” and 44% as “false.”

On climate change, 52% of the survey respondents indicated that they believe scientific evidence supports the proposition that the earth’s temperature has been increasing in “the last few decades” as a result “of human activity such as burning fossil fuels.” Thirty percent indicated that they did not believe there was “solid evidence” of increasing global temperatures over the “past few decades,” while another 18% indicated that they believed there was “solid evidence” of warming but that the cause was “mostly. . . natural patterns in the earth’s environment,” as opposed to “human activity.” These figures, too, are in line with recent national opinion surveys (Silver 2013).

Irrespective of their responses to these items, however, the overwhelming majority of survey respondents agreed with the proposition that the “health benefits of obtaining generally recommended childhood vaccinations outweigh the health risks” (BALANCE). Eighty percent of the respondents who believe in human-caused climate change agreed with this proposition. So did 81% of those who believe the earth’s temperature has increased as a result of “natural patterns,” and 73% of those who believe the earth’s temperature has not increased in recent decades. Eighty percent of the respondents who believe in evolution and 77% who do not  (a difference smaller than the survey margin of error) likewise indicated that they agree the benefits of childhood vaccinations outweigh their risks (Figure 5).

Study participants also responded to items measuring both their religiosity and their knowledge of and facility with scientific evidence. The former was assessed with a scale that aggregated self-reported church attendance, frequency of prayer, and “importance of God” in the respondents’ lives (α = 0.86). Subjects’ “science literacy” was assessed with 11 items from the NSF’s Science Indicator battery, which is conventionally used to study public understanding of science in the U.S. and abroad (NSF 2012). In addition, subjects completed a ten-item version of the Cognitive Reflection Test (Frederick 2005; Toplak, West & Stanovich 2013), which assesses the motivation and capacity to consciously interrogate one’s views on the basis of available information, a critical-reasoning disposition integral to forming evidence-based beliefs (Toplak, West & Stanovich 2011).

The NSF and CRT items formed a reliable scale (Cronbach’s α = 0.82), which can be interpreted as measuring a “science comprehension” aptitude (Kahan, Peters et al. 2012). Consistent with previous studies (Pennycook 2012, 2013; Shenhav, Green & Rand 2011; Gervais & Norenzayan 2012), there was a modest negative correlation between the religiosity and science comprehension (r = -0.26, p < 0.01).

Religiosity and science comprehension also were meaningfully—but not straightforwardly—associated with the study subjects’ positions on evolution and climate change. Science comprehension was modestly associated (r = 0.28, p < 0.01) with belief in evolution and weakly associated with belief in human-caused climate change (r = 0.10, p < 0.01) for the sample as a whole (including both survey and experiment subjects). But the impact was moderated by subjects’ religiosity: among those low in religiosity, higher science comprehension substantially increased belief in evolution and in human-caused global warming; among those high in religiosity, however, higher science comprehension had next to no impact on belief in evolution and substantially reduced belief in human-caused global warming (Figure 7).

The interaction between religiosity and science comprehension is not surprising. Science literacy and critical reasoning dispositions have been found to magnify cultural and ideological predispositions toward global warming (Kahan, Peters et al. 2012; Kahan 2013b). So it stands to reason that they would have the same impact on predispositions associated with religiosity, which plays a comparable role to shared cultural and political outlooks in the web of social relationships that orient individuals toward what is known by science. “Belief in evolution” is not a reliable indicator of either a scientifically literate understanding of evolutionary mechanisms (Schtulman 2006; Bishop & Anderson 1990) or the species of science literacy measured generally by the NSF Science Indicators. Rather, how one responds to the question “do you believe in human evolution” indicates a form of identity that features religiosity (Roos 2012). It is perfectly plausible that the significance of “disbelief” in evolution as an expression of personal identity would be unaffected by science knowledge—or possibly even reinforced by habits of mind associated with critical reasoning. Indeed, experimental evidence supports this inference (Lawson & Worsnop 2006).

These relationships—which are integral to making sense of the salience and ferocity of societal conflict over climate change and over evolution—were absent from the views of the survey respondents toward childhood vaccines (Figure 7). Both science comprehension (r = 0.12, p < 0.01) and religiosity (r = -0.14, p < 0.01) displayed only weak relationships with the battery of items that formed the PUBLIC_HEALTH scale. There was an interaction between religiosity and science comprehension in the survey respondents’ scores on the scale, but it was small in size and, more importantly, moderated only the intensity of the positive orientation that subjects of varying levels of religiosity expressed toward childhood vaccines (App. 1, Table 1).

A more detailed examination of the participants’ responses to the various survey items follows. Unsurprisingly, there is unanimity on none. Nevertheless, understood in relation to contested societal issues that feature conflict among large and readily identifiable societal groups, the uniform and uniformly supportive margins of agreement reflected in survey responses is of fundamental interpretive significance. As will become even more apparent, in probing the nature of opposition to universal childhood immunization, one is necessarily assessing the attitudes of a segment of the population that is small in size and that defies identification by the sorts of characteristics associated with recognizable cultural styles in American society.


To download Vaccine Risk Perceptions and Ad Hoc Risk Communication: An Empirical Assessment, click here.


The logic of reciprocity--and the illogic of empirically uninformed vaccine risk communication

One of the aims of the CCP Vaccine Risk Perception and Ad Hoc Risk Communication study was to examine the impact of empirically uninformed vaccine risk communication.

By “empirically uniformed risk communication,” I don’t mean vaccine-risk misinformation, such as the claim that childhood vaccines cause autism. I take as a given that false assertions like that generate unwarranted public concern.

Rather, I’m using “empirically uniformed risk communication” to denote information that accurately conveys the risks of childhood vaccines--likely for the very appropriate purpose of counteracting misinformation-- but that nevertheless embeds that information in empirically insupportable representations about the extent, sources, and consequences of public unease toward universal immunization.

Disseminated by journalists, advocates, and even some public health professionals, this kind of vaccine-risk communication is the type that ordinary members of the public are in fact most likely to be exposed to.

It’s core message is that public health in the U.S. is being threatened by a “growing crisis of public confidence” in vaccines.  No longer confined to “[t]he fringe who don’t believe in medicine for religious reasons,” a “growing distrust of vaccinations” is now sweeping across “our nation’s parents,” we are told (& told & told & told).

The resulting “erosion in immunization rates” is predictably ... leading to the resurgence of diseases considered vanquished long ago” including whooping cough and measles. “From Taliban fighters to California soccer moms,” one source concludes, “those who choose not to vaccinate their children against preventable diseases are causing a public health crisis.”

The CCP study didn’t purport to test these claims. Instead, it deferred to sources that employ valid empirical methods specifically suited to measuring immunization rates and the incidence of childhood diseases.

These sources belie the claim that vaccination rates are declining at all, much less “eroding.”

According to data compiled by the U.S. Centers for Disease Control, coverage for recommended childhood immunizations—including MMR, pertussis, Hepatitis-b, and polio—have all been holding steady at or above 90% (the target threshold) for well over a decade (CDC 2013a, 2008, 2006). The proportion of children receiving no vaccinations has persisted at or below 1%, despite the ready availability of nonmedical “exemptions” from state-administered universal immunization policies for objecting parents.

Rather than a “large and growing number” of “otherwise mainstream parents” refusing to vaccinate their children, the CDC reports (in annual press releases, the language of which varies little from year to year) that“ ‘nearly all parents are choosing to have their children protected against dangerous childhood diseases’ ” (CDC 2010)

There are local enclaves, the CDC cautions, in which vaccination rates are significantly lower than the national average. These enclaves are often the site of recurring localized outbreaks of diseases, like measles, which public health officials have deemed eliminated in the United States but which can be introduced into such communities by individuals infected during travel abroad (CDC 2013b).

Fortunately, “[h]igh MMR vaccine coverage in the United States (91% among children aged 19–35 months),” the CDC states, “limits the size of [such] outbreaks,” which averaged 60 cases per year over the last decade (ibid.).

The incidence of whooping cough, which has not been eliminated in the United States, is also likely higher in low-vaccination enclaves (Atwell et al. 2013; Glanz et al. 2013; Omer et al. 2008). But “[p]arents refusing to get their children vaccinated,” according to the CDC, are “not the driving force behind the large scale outbreaks” of this disease in recent years (CDC 2013c). In addition to “increased awareness, improved diagnostic tests, better reporting, [and] more circulation of the bacteria,” the CDC (2013c) has identified “waning immunity “from an ineffective booster shot as one of the principal causes, a view shared by public health experts (Cherry 2012).

Pockets of resistance to vaccination pose a serious and unmistakable public health concern. They merit considered attention informed by empirical methods suited to assessing the influences that generate them, the contributions they make to the incidence of childhood diseases, and the measures that might be employed to counteract and contain them (Opel 2011, 2012; Mnookin 2011; Omer et al. 2008).

But the existence of anti-vaccine enclaves and the dangers they pose do not furnish empirical support for asserting that there is a “growing crisis of public confidence” in childhood vaccines, that “immunization rates with MMR have dropped in . . . the US,” or that a “rising tide of … vaccine reluctance” has generated “a resurgence of diseases gone so long that some doctors don’t even recognize them.

Such claims reflect not an “epidemic of fear” among ordinary parents, but an epidemic of hyperbole among a diverse collection of actors resorting to ad hoc, empirically uninformed alternatives to genuinely evidence-based forms of risk communication.

I'm sure those engaging in empirically uninformed vaccine risk communication are not doing so in bad faith.

Most probably just don’t know what they are talking about—in part because of the prevalence of empirically uninformed vaccine risk communication.

But some probably do realize that they are in fact grossly mischaracterizing the extent of vaccine avoidance in the U.S., and misattributing to it disease outbreaks that in fact stem from other causes such as the ineffective pertussis booster shot.

They probably figure that this fact-disconnected style of risk communication is okay because it will grab people’s attention and stir them to anger at parents who are not vaccinating their children and definitely should be.

But that way of thinking is empirically uninformed, too.  Indeed, the scientific study of science communication suggests that understating the high level of vaccination in the U.S. could actually weaken public support for and cooperation with universal immunization programs.

The “herd immunity” associated with universal childhood vaccination is a collective good (Olson 1965). That is, by complying with universal vaccination policies, parents confer a benefit—reduced risk of contracting a disease—not only on their own children but also on those who as a result of age, medical restrictions, or material disadvantage have not been able to secure the protection that such vaccinations confer.

In collective actions settings—from tax compliance to recycling, from voting to observation of informal norms on picking up one’s children on time from daycare centers—individuals tend to behave like moral and emotional reciprocators (Gintis et al. 2004). That is, rather than engage in purely self-interested calculation, they are motivated to contribute voluntarily to collective goods if they perceive that others are doing so, but to refrain from contributing if they think free-riding is widespread.

This dynamic makes it imperative that people not be induced to underestimate the extent to which others are voluntarily contributing to a collective good. If they do, a higher number of individuals will themselves refrain from contributing—behavior that can be expected to induce others to do the same, generating a self-reinforcing spiral of non-cooperation (Kahan 2004).

The logic of reciprocal cooperation implies that people who believe that others are refraining from getting vaccinated and instead free-riding on the contributions of others to herd immunity will themselves be less willing to get vaccinated. One experimental study using self-report data suggested that students exposed to information that suggested other students were forgoing vaccination and effectively free-riding on the decisions of others to get their flu shots responded in exactly this way (Hershey et al. 1994).

The results of CCP Vaccine Risk Perception study suggest that members of the general public substantially underestimate childhood-vaccine coverage. Asked to estimate “about what percentage of U.S. children (age 19-35 months) received the recommended vaccinations for childhood diseases” in recent years, only 9% of the survey subjects indicated “90% or above”; the median estimate was “70-79%.” In addition, approximately 40% of the sample indicated that the “trend in the rate of vaccination for U.S. children (age 19-35 months)” had gone down either “a little” or “a lot.”

The survey participants likewise grossly overestimated the proportion of children who receive no vaccinations. Only 9% correctly put the figure at “1% or less.” The median response was “2%-10%.” Over one-third of the sample selected either 11% to 20% or 21% to 30%.

Because of the contribution that reciprocity makes to individuals’ motivations to contribute to public goods like herd immunity, this kind of misunderstanding is not good.

Even worse, the experimental component of the CCP study found that individuals’ levels of misunderstanding grew when they were exposed to empirically uninformed vaccine risk communication.

In the experiment, subjects were assigned to one or another condition, members of which read different materials patterned on real-world media and internet sources.  Those assigned to the “Crisis” condition read a news that assert “growing” parental resistance to vaccination and a resulting decline in vaccination rates. Those assigned to the  “Anti-science” condition read an op-ed commentary that similarly implied that vaccination rates were declining based on fear of vaccine side-effects among individuals disposed to distrust scientific information on issues like evolution and climate change.

Subjects in both the “Crisis” and “Anti-science” conditions underestimated national vaccination coverage.  They also were more likely to report that vaccine rates had gone down in recent years.

Subjects in the “CDC” condition, in contrast, received a news story that quoted CDC officials accurately indicating that “vaccination coverage rates . . . have remained stable at or above 90 percent for over a decade,” and that “less than 1% of toddlers had received no vaccines at all,” but also warning of the “the existence of local communities in which vaccination coverage is lower than target levels for certain diseases