Thinking About Evolution: Cognitive Factors That Get in the Way

Originally posted on the old blog on 3/12/2006

My contribution to Darwin Day was pretty weak for a staunch supporter of science. Sure, I think the name is a bad idea, and want to rename it "Evolution Day," or at least something other than Darwin Day (I thought about maybe suggesting "Variation Appreciation Day," or "Hug a Mutation Day"). But objections to the name aside, I felt kind of guilty about making such a substanceless contribution to a day with what I believe are noble purposes, especially after reading (via Clark) that 53% of Americans reject evolution entirely. So I'm going to try again. This time, I'm going to approach evolution from a cognitive scientist's perspective. That means I'm going to try to answer the question, how do people think about evolution? I suspect that most of the readers of this blog realize how important a question that is, given how many people in this country reject evolution, often as a result of gross misconceptions. Education researchers certainly realize its importance, and as a result there is a large literature on evolution education, and how students understand the central concepts in evolutionary biology like natural selection, adaptation, inheritance, and so on. The short answer to the question from that literature, which I doubt will surprise anyone, is that most people don't think about evolution very well. In fact, it almost as though Dawkins' quip from The Blind Watchmaker that "it is almost as if the human brain were specifically designed to misunderstand Darwinism and to find it hard to believe" isn't that far off. In this post, I'm going to try to explain a few of the reasons why that is.

Evolution education is an interesting case for education researchers and cognitive scientists because there are so many of what you might call non-epistemic factors at play. For example, a study by Brem et al. a few years ago found that across the spectrum from creationist to evolutionist, college students tended to believe that evolution will have negative psychological and social consequences¹. It's likely that for many, belief in these negative consequences influences not only their willingness to believe in evolution, but also their willingness to expose themselves to information about it, or to attempt to understand that information. There are also many social or familial factors at play. To explain differences in the developmental paths towards creationism vs. evolutionism, Margaret Evans has proposed a "model of constructive interactionism," in which "children generate intuitive beliefs about origins, both natural and intentional, while communities privilege certain beliefs and inhibit others, thus engendering diverse belief systems"². In other words, children come to the table with certain intuitions about the origins of things (I'll discuss those intuitions in a bit), and socialization and education processes serve to encourage some of those intuitions while de-emphasizing others. Thus, children in strong creationist families will have their intuitions that are directly opposed to evolution encouraged, making the job of science educators even more difficult. In this post, I'm going to describe three of of the intuitions and biases that are directly relevant to how children and adults think about evolution, because I find them to be the most interesting.

Intuitive Theists

There is a growing body of evidence indicating that children are inclined to view both artifacts and natural kinds (biological and non-biological) as existing for a purpose, and to believe that they were intentionally created for that purpose. Here is Deborah Kelemen describing some of the research indicating children's inclination to believe that natural kinds have a purpose³:

Consistent with the view that from very early on, teleological assumptions constrain our reasoning about living things, studies have found that young children attend to shared functional adaptation rather than shared overall appearance (or category membership) when generalizing behaviors to novel animals (Kelemen et al., 2003a), judge whether biological properties are heritable based on their functional consequences rather than their origin and explain body properties by reference to their self-serving functions not their physical-mechanical cause.

The objects to which children will attribute a purpose range from animal parts (e.g., legs are for walking) to whole animals (lions exist "to go in the zoo"), and even non-biological kinds (clouds exist to make rain). In addition, when asked whether someone created the first of a particular item, children are likely to answer yes for all three kinds of objects (artifacts, biological kinds, and non-biological natural kinds)⁴. It's understandable, then, why evolution should be difficult to teach to children: it is counterintuitive. Both the non-teleological aspects of evolutionary explanations of the origins of biological kinds, and the lack of a need for an intelligent designer go against children's natural view of things.

But the story is actually somewhat worse for evolution than intuitions about purpose and intentional creation indicate. While evolution involves non-teleological processes, teleological language is still pretty common in discussions of evolution (even Darwin used it), and many adults who believe in various intelligent design philosophies insist that the intelligent design position is not inconsistent with evolutionary biology. But children's intuitions may be more specific than simply inferring teleology and purposeful creation. They may actually be creationists, at least at certain ages. Margaret Evans has explored the beliefs of children in both fundamentalist Christian and non-fundamentalist households, and found an interesting, and for educators, somewhat disturbing pattern⁵. In her study, children under the age of 8 in fundamentalist households tended to be strict creationists: they believed that a non-human intelligent entity (God) created all animals as they are now, while children under the age of 8 in non-fundamentalist homes held beliefs that Evans describes as a mixture of creationism and "generationist" origins (such as "the first robins came from eggs); between the ages of 8 and 10 years, children were strict creationists, regardless of the type of household; and from 11 on, children in fundamentalist households tended to be strict creationists, while children in non-fundamentalist homes tended to be evolutionists. Thus it appears that education can, in older children, overcome creationist intuitions, but only if that education is consistent (or at least not inconsistent) with what children are being taught in the home.

The work of Kelemen and Evans helps to explain why evolution has had such a hard time becoming widely accepted by the general public. From an early age, our intuitions run counter to evolutionary science, and unless children live in homes where evolution is not seen as being counter to the belief systems of their parents, they will not let go of those intuitions, even when they are taught about evolution in school. Those children will then go on to privilege those same intuitions in their children, and so on, leading to generation after generation of individuals who, by the time they are college-aged, will find it very difficult to accept any evolutionary teachings.

Intuitive Essentialists

In what's now a classic paper, Medin and Ortony⁶ argued that humans may be intuitive essentialists. They called this position "psychological essentialism," and there is a growing body of evidence indicating that they were right. We are essentialists, especially about natural kinds, and biological kinds in particular, from a very young age. It may not seem so at first, but this fact could have very important implications for evolution education, and the willingness, perhaps even the ability, of many people to accept evolution as an explanation of biological origins.

Here is how Gelman and Markman expressed what later became the psychological essentialism position⁷:

Natural kinds are categories of objects and substances that are found in nature (e.g., tiger, water, cactus)... natural kind terms capture regularities in nature that go beyond intuitive similarity... Natural kinds have a deep, nonobvious basis; perceptual features, though useful for identifying members of a category, do not always serve to define the category. For example, "fool's gold" looks just like gold to most people, yet we accept the statement of an expert that it is not gold... Because natural kinds capture theory-based properties rather than superficial features, some of the properties that were originally used to pick out category members can be violated, but we still agree the object is a member of the kind if there is reason to believe that "deeper," more explanatory properties still hold. (p. 1532)

In other words, people believe that natural kinds have an underlying, unseen essence that makes them what they are, and that while this essence is likely associated in some causal fashion with the surface features that we usually use to classify an instance of a kind, the essence remains the same regardless of whether the surface features change. For biological kinds, people (including young children) believe that origins (who the parents were) determine the essence of an individual. Thus, when an animal born as a raccoon, to raccoon parents, is painted too look like a skunk, and has a sack containing a stinky substance surgically implanted, children still call it a raccoon⁸. This belief has implications for how people make inferences about biological kinds, including inferences about origins. For example, in a study with adults, participants heard a story about a fictitious animal, called a "sorp," that has all the prototypical features of a bird (feathers, makes nests, etc.). In the story, the "sorp" falls into a vat of toxic waste, and all of its perceptual features change: its feathers are gone, and it now has wings that look like insect wings, has an insect-like exoskeleton, and so on. It now looks like an insect, not a bird. As the story moves along, the insect-like sorp mates with a normal sorp. The participants were then asked whether the offspring of the changed and normal couple will have insect-like or bird-like offspring. They overwhelmingly indicated that the offspring would be more bird-like⁹.

In a paper published in this month's issue of Cognitive Psychology¹⁰, Andrew Shtulman argues that essentialist thinking may have implications for how people understand evolution. He writes:

Applied to the study of biological adaptation, essentialism led early evolutionary theorists to commit what Gould (1996) calls the "fallacy of reified variation," or the tendency "to abstract a single ideal or average as the essence of a system and to devalue or ignore variation among the individuals that constitute the full population" (p. 40). These theorists construed evolution as the process by which a species' essence is transformed over time, and they proposed a variety of essence-transformation mechanisms, including the inheritance of acquired traits (Lamarck, 1809), the unfolding of a preprogrammed design (Chambers, 1844), the recapitulation of ontogeny (Haeckel, 1876), the acceleration of growth (Cope, 1896), the chemical structure of protoplasm (Berg, 1926), the lawful properties of organic matter (Eimer, 1898), the intentional properties of intelligent systems (Butler, 1916), and an élan vital (Bergson, 1911). (pp. 172-173)

Shtulman lumps these positions together under the heading of "transformationalism." Darwin, Shtulman argues, was so important because he was able to overcome the intuitive essentialist thinking that dominated the work of these and many other natural scientists, and thus overcome transformationalism. His theory embodies what Shtulman calls variationism, which he describes as (referencing the figure below):

First, chance mutations and sexual recombinations create indidifferencessrences among members of the same species (depicted in the left handfthand panel of Fig. 1 as arrows between parents and offspring of different colors). Second, some of these individual differences are retained and others are eliminated on the basis of their utility to survival and reproduction (depicted by circles around the few organisms that produce offspring.

Shtulman illustrates the differences between the two positions with this diagram:

Notice how in the transformationalist diagram, the color of some of the moths changes slowly over generations (presumably to a more and more adaptive color), while in the variationist diagram, one-time mutations create variability in the population of moths that is passed on from generation to generation, with the new color becoming more common in the population because it is more adaptive.

Most of us, unfortunately, are not Darwins, and overcoming such deeply ingrained intuitive biases may not come easy to us, even after years of science education. Shtulman presents data in his paper showing that both high school and college students (though not evolutionary biologists), tend to consistently give transformationalist answers to questions about origins and adaptation. Thus, it appears that in a very important way, our intuitive essentialist beliefs about biological kinds make it difficult for us to understand how evolution works.

The Value of Beliefs

Many factors man contribute to the value of particular beliefs. Howevrecentecents study by Jesse Preston and Nicholas Epley¹¹ demonstrates two factors that may be of particular importance in the relationship between evolution and some religious beliefs (e.g., those held by 53% of the American public, according to the survey linked above). They showed that when people are asked to explain things with a belief, the perceived value of that belief goes up, whereas when people are asked to explain a belief, the perceived value goes down. They interpret this as showing that the value of a belief is, at least in part, determined by its position in a causal or explanatory sequence. If the belief explains a lot of other facts and beliefs, then it is valuable, whereas if it is explained by other facts or beliefs, it becomes less valuable. In one of their experiments, they explicitly looked at what they called "cherished beliefs," in this case, beliefs about God. Participants were divided into four groups. Two groups were asked to list things that belief in God could explain, with one group asked to give three and one ten things. The other two groups were asked to list either 3 or 10 observations that could explain God's "behavior." Overall, participants who believed in God (self-reported atheists were excluded) had a difficult time listing observations that could explain God's behavior, but when they did, whether they listed 3 or 10, their ratings of their belief in God were lower than the participants in the applications conditions. Preston and Epley argue that the difficulty participants had in providing observations that explain God's behavior may be a result of the fact that people have a hard time coming up with explanations for highly valued beliefs, because these explanations would devalue beliefseleifs.

The implications of these findings for evolution education should be obvious. For many who believe that God produce biological kinds, and humans specifically, in their present form, an alternative explanation, even if it is possible to say that it was the work of God, will serve to devalue that belief, by relegating it to a lower position in the explanatory system. Thus, the very nature of our relationship to beliefs we hold valuable may make evolution education more difficult, particularly for people raised in in fundamentalist traditions.

Conclusions

So that's my contribution. I've presented three factors that make the job of biology teachers more difficult when they're trying to teach evolution, either to children or adults.

1. Intuitive theism, in which our intuitions lead us to make design inferences about complex kinds or under conditions of uncertainty; intuitions that can be reinforced culturally to an extent that it may be almost impossible to overcome them by the time we reach adulthood.
2. Intuitive essentialism, which causes us to believe that biological kinds have hidden internal essences which determine what they are, how they will behave, and what features they should have, and which may make us interpret evidence of adaptation in transformationalist, rather than Darwinian/modern biological varationist terms.
3. The role of explanatory power in determining the value of beliefs, and the fact that we may resist explaining our most cherished beliefs in order to avoid devaluing them.

There are probably more cognitive factors that make understanding and believing modern biological accounts of evolution difficult for many people, but these three together, or alone, can pose significant challenges, and each should be in the backs of educators' minds when teaching people about evolution. To be honest, I'm not sure how to overcome the third factor. As recent world events have shown, when beliefs are as cherished as religious beliefs are for many, defense of those beliefs against any perceived threat can be extremely passionate, even violent. If many people really do perceive that the potential explanatory power of evolution could pose a threat to the value of their religious beliefs about the origins of man, beliefs that they cherish deeply, it's unlikely that any amount of education will overcome their defensiveness. But the prospects of overcoming the first two factors do seem promising. Clearly many biologists (including three who completed the questionnaire in Shtulman's study were able to overcome their transformationalisttnalist bias caused by their intuitive essentialism (see also this paper, by Evans and her colleagues, on one technique for overcoming essentialist biases in children), and Evans' work on intuitive theism indicates that, as long as parents aren't encouraging theistic intuitions, thus making us skeptical or resistant to evolutionary accounts of origins, our seemingly innate tendency to make design inferences can be overcome through education.

¹Brem, S.K., Ranney, M., & Schind, J. (2002). Perceived consequences of evolution: College students perceived negative personal and social impact in evolutionary theory. Science Education, 87(2), 181-206.
²Evans, E.M. (2001). Cognitive and contextual factors in the emergence of diverse belief systems: creation versus evolution. Cognitive Psychology, 42(3), 217-266.
³Kelemen, D. (2004). Are children 'intuitive theists'?: Reasoning about purpose and design in nature. Psychological Science, 15(5), 295-301.
⁴Kelemen, D., & DiYanni, C. (2005). Intuitions about origins: Purpose and intelligent design in children's reasoning about nature. Journal of Cognition and Development, 6(1), 3-31.
⁵Evans, E. M. (2001). Cognitive and contextual factors in the emergence of diverse belief systems: Creation versus evolution. Cognitive Psychology, 42, 217-266.
⁶Medin, D. L., & Ortony, A. (1989). Psychological essentialism. In S. Vosniadou & A. Ortony (Eds.), Similarity and Analogical Reasoning, Cambridge, 179Ã?-195 .
⁷Gelman, S.A., & Markman, M. (1986). Young children's inductions from natural kinds: The role of categories and appearances. Child Development, 58, 1532-1541.
⁸Keil, F.C. (1989). Concepts, Kinds, and Cognitive Development. Cambridge, MA: MIT Press.
⁹Rips, L. J. (1989). Similarity, typicality, and categorization. In S. Vosniadou & A. Ortony (Eds.), Similarity and Analogical Reasoning. Cambridge, England: Cambridge University Press, pp. 21-59.
¹⁰Shtulman, A. (2006). Qualitative differences between naïve and scientific theories of evolution. Cognitive Psychology, 52, 170-194.
¹¹Preston, J., & Epley, N. (2005). Explanations versus applications: The explanatory power of valuable beliefs. Psychological Science, 18, 826-832.