MAPKIA #73 part IV: Revenge of the disgust skeptics! Does *disgust* really play any role in vaccine & GM-food risk perceptions?
So I’ve spent a day or so reflecting on the really great Wendell & Clifford guest post, along with their fantastic “in press” paper, on disgust sensibilities and vaccine-risk and GM-food risk perceptions. I learned a ton from doing so.
I have some questions, certainly.
But in my experience, the best studies are always the ones that make you pay for the solution to a vexing puzzle by obliging you to see multiple additional ones that you now feel impelled to find an explanation for. That's the way I feel about W&C's post & paper.
I’ve divided my reactions into two parts. The first set address W&C’s own data, the second their “alternative interpretation” of the data analyses that earned @Mw her now disputed 5th straight MAPKIA! crown (the Chair of CCP Gaming Commission has stripped her of the synthetic biology giganto E. coli first prize. . . heart breaking . . .).
A. W&C's data
1. High or low, disgust sensitivities predict a high level of support for vaccines, no? Unlike a lot of researchers, W&C don’t hang their hat on disembodied correlation coefficients with long strings of asterisks. They get that a “statistically significant” correlation is not equivalent to a practically meaningful influence. They respect the reason of readers by showing them the raw data, so that readers can meaningfully reflect on whether they agree the relationship expressed in the correlation bears the interpretation—because that’s inevitably what it is!—assigned to it.
I certainly respect and value the account they give to support their conclusion.
But when I look at the cool W&C data, I infer that people who vary in “pathogen” disgust are not in much disagreement: childhood vaccines are a good idea.
W&C don’t describe the wording of the individual survey items used to from the “opposition to vaccines” scale, but their scatterplot does make it possible for us to see that all the subjects in their sample are heavily concentrated at the lowest values of “opposition.” In other words, across the items, the sample was highly skewed toward responses the evince “support” for vaccines.
Even the individuals who scored high on the “pathogen disgust sensibilities” (PDS) scale were many times more likely to hold a positive than a negative attitude toward vaccines. The “r = 0.15” (students) and “r = 0.20” (M turk) coefficients, then, don’t bear out the inference that high-PDS subjects were afraid of or against vaccines; they imply only that the high degree of support that those subjects had for vaccines wasn’t quite as high as was that of subjects low in PDS.
Just to try to add some perspective to the admirably concrete picture W&C show us, consider these data from the CCP Vaccine Risk Perceptions and Ad Hoc Risk Communication Report:
These are the sort of data that make it possible to see that those who think that there is meaningful ideological contestation over vaccine risks are uninformed (to put it politely). Yes, subjects who are more left-leaning in their outlooks love vaccines a smidgen more than those who are right-leaning. But it is clear enough that those who are “right-leaning” love them too!
The correlation between this item and left-right ideology (r = -0.14) is about the same one that W&C report in their student sample.
The correlation that W&G report in their other M Turk subjects—r = 0.20—is a bit higher.
But here is what an "r = 0.20" relationship looks like in raw data relating the Industrial Strength Risk Perception measures for childhood vaccines, and in comparison to perceptions of a bunch of other putative risks (again from the CCP Vaccine Risk Perceptions and Ad Hoc Risk Communication Report):
The point of showing the data that stand behind disembodied “statistically significant” correlations is to see whether they support the inferences that people draw from them.
Just as I think it would be unreasonable for someone to treat these CCP data as saying “conservative ideology predicts fear of” or “opposition to” to childhood vaccines, so I think it is not persuasive to treat W&C’s data as suggesting that high pathogen-disgust sensitivities predict any sort of opposition to or concern about childhood vaccines in either their M Turk or student samples.
Indeed, in their excellent paper, W&C characterize the relationship between PDS and the perception that vaccines cause autism as "weak and not statistically significant” (p. 26) for their student subjects.
2. Inferential sufficiency? W&C show us that pathogen-disgust sensitivities are correlated, but not very strongly, with both GM-food and vaccine risk perceptions. But that’s not actually enough information for us to assess whether either, much less both of these risk perceptions, are meaningfully explained by variance in disgust sensitivity.
Before we can draw that inference, we'd need to be shown, first, that the relationship between PDS and both GM-food and vaccine risk perceptions is comparable to what we’d expect to see between PDS and the perceived risks of other putative risk sources that we are already confident do provoke pathogen-disgust reactions. If the relationship is smaller, then that’s a reason for thinking that disgust sensitivities aren’t that important in the case of GM-food and vaccine-risk perceptions.
Second, we’d need to be shown what the relationship is between PDS and other putative risk sources that we have good reason to believe don’t provoke meaningful pathogen disgust sensitivities. If those relationships are comparable in size to those between PDS and either GM-food or vaccine-risk perceptions, that would be reason, too, for discounting the inference that GM-food and vaccine-risk perceptions are meaningfully “explained” by differences in pathogen-disgust sensitivities.
This was the nub of @Mw’s case against treating disgust sensitivities as linking GM-food and vaccine-risk perceptions. The relationship between the two was the same as the one between each of those risks and myriad other risk perceptions of putative risk sources, like drones and nuclear power, that didn’t seem to have much to do with disgust.
W&C don’t present this sort of info—the equivalent of what one would need to fill in a 2x2 covariance matrix—in the blog post, but they do have some data on other risk perceptions in their excellent paper.
Others should look and see what they think, but I found this data somewhat puzzling.
E.g., they report that neither drugs nor cigarettes, which they say are recognized in the literature as exciting pathogen-disgust sensitivities, seemed to have meaningful relationships with PDS in their sample. Indeed, they reported that sexual- disgust sensitivities were more meaningfully associated with anti-drug attitudes in their sample than pathogen disgust ones!
If the disgust scale didn’t perform as we expected on risk perceptions that we think we are related to disgust, then I’m left confused about what to make of the (pretty modest) relationships that they report between the scale and attitudes toward vaccines and GM foods.
Perhaps this is something W&C can clarify in a follow up or in fact do address in a revised version of the paper.
3. Why aren’t conservatives disgust sensitive? I found it remarkable that there was no meaningful correlation between PDS and ideology in the W&C sample. The idea that conservatives are “disgust sensitive” is a big theme in the moral psychology literature; the claim is made about “pathogen” as well as “sexual disgust” sensitivities.
I’d surmise that atypicality of the M Turk subjects, whose ideologies (W&C report) were heavily skewed toward liberalism, might have something to do with the explanation, except that on Twitter, Clifford supplied data showing that PDS had no meaningful relation with ideology in a YouGov sample, which I presume was drawn from a sample recruited and stratified for national representativeness.
I gather that “sex disgust sensitivities” (SDS) are generally understood to have a higher correlation with conservatism than PDS ones. But the two are supposed to be correlated. That, plus the W&C results on the relationship between SDS and drug laws, and the very modest relationships reported in studies that do seem to show an ideological-disgust relationship, have now made me wonder whether the relationship between disgust and conservatism is as meaningful as it is made out to be by many commentators.
I’m sure moral psychologists will sort all this out!
B. @Mw's "factor 1"
1. Who sees what as a “pathogen” and why? I myself was not entiredly persuaded that the loading of GM food risks on @Mw’s “factor 1” supports W&C's inference that variance in GM foods is explained by PDS.
For one thing, it seems ad hoc to treat the eclectic assortment of risks that happened to load on “factor 1” as evincing a latent PDS sensibility.
Why did “residential exposure to magnetic field of high-voltage power lines” (POWER) and “user exposure to radio waves from cell phones” (CELL) load on factor 1?
But then why didn’t nuclear power load on that factor? The idea that nuclear power plant radiation is hazardous is in fact a much more conspicuous, much more contentious matter in our society than that either cell phones or high-voltage power lines harm anyone.
Why didn’t “fracking”—which involves injecting noxious chemicals into bedrock, where it can leach into the groundwater—load on “factor 1” if it is measuring a latent PDS sensibility?
Again, drug use is generally understood in the literature to excite PDS. So why didn’t marijuana legalization load on “factor 1”?
What about "drinking raw milk (milk that has not been pasteurized)" (RAWMILK)? That stuff is brimming with delicious E. coli, salmonella & other pathogens. Shouldn't it load on Factor 1 if Factor 1 is about "pathogent disgust" sensibilities?
“Private operation of drones in U.S. airspace” (DRONES) correlates more strongly with “Factor 1” (r = 0.20, p < 0.01) than does raw milk (r = 0.09, p =, p < 0.01). That’s weird, I think, if the factor is supposed to be measuring some generic anxiety about bodily invasion by foreign agents (there are some really small drones--they’re adorable!--but none will make it very easily into your blood stream!).
I suggested that “factor 1” is a catchall: there isn’t much public concern about any of the risks that load on it, including consumption GM foods, in the US general public. What explains variance in them is just some unobserved disposition to worry about things not many other people do.
But I accept for sure that there might be more to it.
Indeed, one possibility that occurs to me is a weak form of “environmental risk” sensitivity that is associated with being culturally egalitarian.
Actually, I don’t have cultural outlook scores in this dataset!
But I do have right-left ideology, which is correlated with being egalitarian and communitarian and definitely is an indicator of environmental-risk concern.
I also have the Ordinary Science Intelligence scale.
When I regress “factor 1” on those two variables and their interaction, it turns out that being more “left-leaning” predicts a higher level of the “factor 1” latent risk concern.
Moreover, the disposition to worry about the Factor 1 risks becomes even more politically polarized as science comprehension does—a sign that identity-protective reasoning played a role in the formation of the relevant risk perceptions.
So there’s an explanation that competes with catchall: an environmental risk concern that is characteristic of an egalitarian-communitarian identity but that is less proximate to that identity than concerns about the more culturally freighted risks that figure in “factor 3.”
The effects are not big at all. But given that “conservatives” supposedly have greater PDS, it’s hard to reconcile these data with the proposition that “factor 1” is measuring a risk sensitivity related to pathogen disgust sensitivities.
Unless, of course, “disgust sensitivities” are themselves programmed by cultural outlooks, in which case, contrary to “moral foundations theory,” we’d expect disgust sensitivities to be symmetric with respect to cultural outlooks or political ideologies but to attach to different putative risk sources in patterns that reflect the cultural meanings that the sources in question have for the types involved.
(A last point: the @Mw “factors” were rotated so that they would be, or be close to, orthogonal. Accordingly, it is not really useful to compare the correlations of the factors to one another, as @W&C had helpfully suggested. Nevertheless, if we do that, it turns out that “factor 1” is in fact more strongly correlated (r = 0.13, p < 0.01) with “factor 3,” the “white hierarchical male” risk-skepticism group, than with “factor 2” (r = 0.05, p = 0.02), the social-deviancy “disgust” factor.)
2. No one sees vaccines as a “pathogen.” In any case, as @W&C note, vaccine risk perceptions do not load on “factor 1.” So if “factor 1” is a latent PDS sensibility, concern over vaccines isn’t associated meaningfully with PDS.
W&C suggest that maybe vaccines, because they confer health benefits as well as risks, might not excite PDS. That sounds like a reason for thinking the hypothesis—that people who are vaccine hesitant are motivated by their disgust with needles in their veins—is false, not a reason to think the industrial strength risk perception measure for vaccine risks isn’t a valid measure of vaccine risk perceptions.
For sure the industrial strength measure is a valid indicator of the general affective orientation that people have toward vaccines, ones that informs all manner of assessment they make about vaccine risks and benefits. That's another of the findings from the CCP Vaccine Risk Perceptions and Ad Hoc Risk Communication Report).
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So those are some of the thoughts & questions that occur to me. Thanks a ton to W&C for making me both better informed and more perplexed!
[Note: I'm closing off comments here so that the discussion of W&C's own analysis occurs in 1 place-- after their post.]