During a conversation with Nick Matzke he asserted that Creationists weren't less intelligent necessarily. I contended that they were less intelligent. I based on this on snooping through the GSS when I was posting about the association between lower educational attainment and intelligence and religious fundamentalist & Biblical literalism. There are several variables in the GSS which ask respondents about their views on evolution, and the more intelligent and educated a person is the more likely they are to accept evolution. But this prompts a question:
is this association simply due to confounds of variables?
In other words, the association between intelligence and acceptance of evolution is simply a byproduct of other correlations. If it was not a byproduct of other correlations, one would expect that even among fundamentalists higher intelligence would predict acceptance of evolution. To probe these questions I looked at some very specific variables in the GSS. Of the evolution related questions, SCITEST4 has the largest sample size. It's also rather straightforward, as it offers the assertion that "Human beings developed from earlier species of animals." This is a human evolution question, which I think tends to set a somewhat higher bar than a more generic evolution query. The responses are: Definitely True, coded as 1 Probably True, coded as 2 Probably Not True, coded as 3 Definitely Not True, coded as 4 The numeric equivalents are important. In short, lower values are more "pro-evolution" and higher values more "anti-evolution." It is a convenient ordinal spectrum. So we'll think of it as a dependent variable where higher values indicate greater anti-evolutionism. The predictors or independent variables I'll be looking at are: WORDSUM = number 1 out of 10 correct on a vocabulary test DEGREE = highest educational attainment, 0 = less than secondary education, 4 = graduate (so again, an ordinal interpretation is valid) POLVIEWS = 1-7 from most liberal to most conservative FUND = 1-3, Fundamentalist, Moderate and Liberal BIBLE = 1-3, Bible as Word of God, Inspired or Fable (and yes, some of these independent variables aren't that independent from each other, for example the last two and the first two....) First, let's look at all respondents in the sample...
The Y axis here is the mean value on a 1-4 scale in terms of attitudes toward evolution, with higher values indicating rejection and lower values acceptance. The X axis is straightforward; the number correct on the vocabulary test on a 0-10 scale. If in a particular class everyone accepted that evolution was definitely true the mean value would obviously be 1. If half believed it was probably true, and half definitely true, the mean value would be 1.5. And so on. The trend here is rather clear: the less intelligent are generally skeptical of human evolution (their mean value is closest to "Probably Not True") and the most intelligent are most accepting of human evolution (mean value approaching "Probably True"). This is what I expected. But of course even if there is a correlation that doesn't mean that intelligence is driving this relationship. OK, let's switch to educational attainment:
Because I dropped all classes where N < 50 the bottom of the distribution is cut off for those who have some college education or more. I lumped those with only secondary education or less, and those with some college or more. This increased the sample sizes for any particular class. Note here that the effect of intelligence is much more noticeable in the more educated group; even when you separate those with graduate school educations the effect is there. On the other hand the less educated sample shows little effect of intelligence on skepticism or lack of in regards to human evolution. I suspect that this tells us that the effect of intelligence, if it exists, is very conditional on the population segment. Next, let's move to politics:
Two major results from this. First, greater intelligence seems to correlate with higher rates of acceptance of evolution across the political spectrum. But, the effect is much more powerful among liberals than among moderates than among conservatives. This relates to the second point: at lower levels of intelligence there is relative convergence at some skepticism toward evolution. The difference between the groups is due in large part to the huge variance at the very highest levels of intelligence. The most intelligent conservatives have similar views to the less intelligent liberals. So far I've hit the variables which seem only indirectly related to why someone would reject human evolution. I've argued before based on GSS data that the conservative rejection of evolution is more about the representation of religious conservatives among political conservatives than conservatism entailing creationism as such. So let's look at a religious variable, fundamentalism:
In this case "Liberal" does not refer to politics but to religion. This makes sense, since there have been religious liberals who are political conservatives or to the right-of-center. The Republican successor to Teddy Roosevelt, William Howard Taft, is an exemplar of this category. The first thing that jumps out is that there doesn't seem to be an effect of higher intelligence on Fundamentalists. And there is a somewhat stronger effect of religious Liberalism than Moderation. Again, as with politics you see that the chasm between the groups gets really big the higher you go up the ladder in intelligence. In fact the less intelligent religious Liberals and Moderates actually lean a bit to the human evolution skeptic side. Finally, we get to a variables that addresses Biblical literalism. This is the heart of the matter in many ways; a priori one would assume that those who would believe that the Bible was the literal word of God would be very skeptical of human evolution since a plain reading seems to refute that position. And that is what we see:
What jumps out at you? To me it is that more intelligent literalists are more skeptical of evolution than the less intelligent! This makes sense, doesn't it? If you aver that the Bible is the literal word of God the brighter you are the more internally coherent you want to be because systematic relationships inferable from presuppositions are obvious. And again, note that even among those who believe that the Bible is a book of fables, and so reject its role as a descriptive model of the universe revealed from a divine being, the less intelligent exhibit more skepticism of evolution than the more intelligent. From these data I conclude that it seems that ideology, group identification and social conformity probably has more to do with how plausible one finds human evolution than intelligence. Granted, as you can see, intelligence remains powerfully predictive for some subgroups, but it is not a significant predictor in other groups. All the variables above have interpretations in an ordinal sense. For example, Fundamentalist, Moderate and Liberal are on a spectrum. But, aside from WORDSUM, one doesn't have a real natural quantitative interval on these variables. Nevertheless, I decided to get a qualitative feel for how the independent variables could predict attitudes toward evolution as the dependent variable. Since this isn't totally kosher, I'm not going to give you the values, but just note that WORDSUM is not very predictive across the whole sample and is not statistically significant in terms of its deviation from 0 in its beta. DEGREE, educational attainment, does have a significant beta, which is non-trivially smaller than POLVIEWS, political orientation, and FUND, the fundamentalism spectrum. The largest effect is from BIBLE, which is one we might assume intuitively. Of course, if I constrain the sample to only a particular class (e.g., religious Liberals) then WORDSUM does turn into a statistically significant predictor. And this last point is one I think which is worth keeping in mind. If you are a person who is liberal in orientation and you interact mainly with other liberals, then you will naturally see a strong relationship between intelligence and acceptance of evolution. If, on the other hand you are very conservative, that relationship will be harder to discern. Finally, if you are a fundamentalist Christian you won't see that relationship in your day to day life. Daniel Dennett's universal acid of Darwinism might not be so universal at all; among liberals it is rather acidic, especially as one goes up the ladder of intelligence and education. Among religious conservatives, far less so. I think it is plausible that the acid can turn one from a religious conservative into a secular liberal, and that is perhaps more to the point of Dennett's thesis, but I think that that generalization elides the reality that social structure remains within our culture. But why is it that the acid needs to burn its way through anything in the first place? Recall that even among those who are very liberal, whether politically or religiously, or who reject the Bible as anything more than fables, there was still a tendency to be more skeptical of human evolution with a lower intelligence. I think part of the issue here is what Paul Bloom addressed in Childhood Origins of Adult Resistance to Science:
The main reason why people resist certain scientific findings, then, is that many of these findings are unnatural and unintuitive. But this does not explain cultural differences in resistance to science. There are substantial differences, for example, in how quickly children from different countries come to learn that Earth is a sphere (10). There is also variation across countries in the extent of adult resistance to science, including the finding that Americans are more resistant to evolutionary theory than are citizens of most other countries (24). Part of the explanation for such cultural differences lies in how children and adults process different types of information. Some culture specific information is not associated with any particular source; it is "common knowledge.".... ...So rather than evaluating the asserted claim itself, we instead evaluate the claim's source. If the source is deemed trustworthy, people will believe the claim, often without really understanding it. Consider, for example, that many Americans who claim to believe in natural selection are unable to accurately describe how natural selection works (3). This suggests that their belief is not necessarily rooted in an appreciation of the evidence and arguments. Rather, this scientifically credulous subpopulation accepts this information because they trust the people who say it is true.
So the rough model is like so: 1) Humans have a natural intuition about the way the universe works which is biased against evolutionary hypotheses. This is why it took so long for these models to ascend to accepted truths even among intellectual elites despite the fact that there were evolutionary ideas extant as far back as the pre-Socratics in ancient Greece. Paul Bloom has reported other research which shows that most young children start out with Creationist biases; but as those in families which accept evolution develop they shed their inchoate Creationist views and accept an evolutionary paradigm. In contrast, those who are raised in Creationist families have their intuitions reinforced through an ideological program where Creationism is offered up as the true and correct alternative to mainstream science. 2) I think it is important to acknowledge that most individuals who do accept evolution do not do so because of the natural and clear obviousness of its postulates and inferences. This is inferable from the fact that most people have only a rough and impressionistic idea of what evolution is. Very few people could elucidate Darwinian theory will any clarity or fidelity, let alone add the nuance of models such as Motoo Kimura's Neutral Theory of molecular evolution. When I was in 7th grade I was going through a test for a gifted program and the psychologist asked what I knew about Darwin's theory of evolution. When I explained my rather primitive ideas there was a long pause, and the psychologist told me that I was the first child he'd interviewed who had given a coherent response which exhibited some understanding of what Darwin had originally said. I don't repeat this to show how well I understood Darwin's theory; I will admit that I have only understood evolution with any great personal degree of confidence for the past 5 years or so. Rather, it illustrates the shallow knowledge base of even those children selected to go through the process of testing for a gifted program. 3) So why the relationship between intelligence and acceptance of evolution among some groups? I suspect that it has to do with identification with peer groups. The extremely intelligent are less likely to trust their own intuition, and receive more reinforcement from peers as to the power and veracity of specialized knowledge producers and providers. If one is, for example, a professional in an abstruse field then it stands to reason that there would be some rational self-interest in ceding to other professionals in abstruse fields the validity of their truth claims. Additionally, those with higher IQs see in their own lives the value which rational and systematic thought can produce, and, that the inferences of such thought are not always plain and obvious from the perspective of someone who relies on introspection and intuition. 4) But, among some subgroups the peer pressures are different. If an evangelical conservative industrial engineer has to pick between his religious identity and the opinions of scientific professionals in academia, it seems not totally implausible that he would select the former. Of course, if you changed it so that the evangelical was a biologist such as Francis Collins then the pressures crank up to a whole new level, and when it comes to evolution group identification with other religious conservatives is not nearly as easy. Conversely, when you have a situation where the peer group is not encouraging even high intelligence may not result in acceptance of evolution. Look at the lack of relationship between intelligence and acceptance of evolution for those who do not go to post-secondary education; my own suspicion here is that being embedded in a dull subculture effects those who are not not dull, just as being a dull person among brights also has an effect. 5) Acceptance of evolution, like science, is about trust for most people. Trust in elites, or trust in your peers, depending on who you are. Very few humans will ever read The Origin Of Species or The Selfish Gene. Similarly, during the 17th century very few educated Europeans personally replicated the observations of Galileo. Rather, Europeans trusted in a system where scholars were attempting to converge upon theoretical truths which mapped to a high degree of accuracy to the world around us. To a great extent the same holds today. 6) The fact that most people who accept evolution have little detailed grasp of its theoretical superstructure implies that they also don't generate many inferences from the model.
