Judith Rich Harris (1995) Individual Differences Within Human Groups. Psycoloquy: 6(40) Group Selection (4)

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PSYCOLOQUY (ISSN 1055-0143) is sponsored by the American Psychological Association (APA).
Psycoloquy 6(40): Individual Differences Within Human Groups

Commentary on Caporael on Group-Selection

Judith Rich Harris
54 Crawford Road
Middletown, NJ 07748



Caporael's (1995) target article discusses four topics in evolutionary psychology. Of these, the most useful is her approach to human social relations and her categorization of human groups into four "core configurations" that vary in size and have different functions. The least useful is her attack on behavioral genetics. Caporael's theory does a good job of accounting for the assimilatory aspects of group membership -- the fact that the members of groups tend to acquire shared patterns of behavior and cognition. However, the theory does not take sufficient account of within-group individual differences.


developmental systems theory, group coordination, group selection, hierarchy, human evolution, social cognition, social identity, teleofunctionalism
1. Caporael's (1995) target article, according to its abstract, "sketches three major topics." These topics are (a) evolution; (b) human social relations; and (c) socially constructed views of reality. A fourth topic, not mentioned in the abstract, is (d) an attack on what Caporael calls "nature-nurture dualism." This commentary will consider all four topics, in that order.


2. "Survival of the fittest" and "natural selection" are vivid phrases that evoke images of the jungle. Caporael would like us to drop these evocative terms and speak instead of "repeated assemblies," a phrase that makes me think of a factory. Clearly, she has an uphill fight ahead of her. How can she convince us that her metaphor is better than Darwin's? Since she is addressing an audience sophisticated enough to realize that "natural selection" does not imply a selector, she can succeed only by showing that "repeated assemblies" makes more accurate predictions or provides more convincing explanations of existing data. As far as I could tell, repeated assemblies does not make any specific predictions and can explain just about anything.

3. There are two problems with the concept of repeated assemblies. The first is its elasticity and vagueness. Caporael starts out by defining the term as "recurrent entity-environment relations" (para. 11), which gives the impression that what is being assembled is an entity and an environment -- an impression reinforced by the example of language as a repeated assembly of a child plus a language environment. But then we have a zygote being assembled from two sources of DNA, and a group being assembled from individuals or from smaller groups, and even breakfast being assembled, presumably from things like toast and orange juice. Can a concept this elastic be useful?

4. The second problem is that the concept of repeated assemblies throws away useful information. The process of evolution is lumped together with the product of evolution (para. 51), and the effects of the genes are lumped together with the effects of experiences. Caporael constructs a model that makes it impossible to distinguish between genetic and environmental effects, and then uses that model to support her claim that the two are indistinguishable.


5. Sociality theory (Brewer & Caporael, 1990) says that humans are social creatures with a long evolutionary history of living in groups, that human psychological mechanisms evolved to meet the social needs of group living, and that these mechanisms sometimes cause humans to put group loyalty above selfish interests. This view is contrasted with what Caporael calls "economic man" -- the view that humans are independent and basically self-interested creatures who will aid others only insofar as the others share their genes. A 1989 paper by Caporael, Dawes, Orbell, and van de Kragt described a series of ingenious experiments designed to refute the "economic man" view; it did the job convincingly. Give humans any excuse at all to think of themselves as a group and they will do so, and thereafter -- whenever group identity is salient -- they will consider the welfare of the group as important, or more important, than their own welfare. (This tendency does not always have benevolent consequences; it is what makes war possible.)

6. Caporael (1995) elaborates on sociality theory by distinguishing four "core configurations" of human groups: dyads, workgroups, bands (or demes), and macrobands. These different sized groups have different functions: in the band (a group of about 30), individuals acquire a social identity and a shared construction of reality; in dyads they develop "microcoordination." I agree with Caporael on this; in fact, I have made a similar distinction (Harris, 1995).

7. However, Caporael goes too far when she tries to find social sources for ALL human cognitive abilities. Thus, she attributes the ability to use tools to the microcoordination acquired in dyadic interactions -- the cognitive mechanism that enables people to use a hammer is the same one that enables them to please a lover. I find this far-fetched. Our ability to manipulate objects has a long evolutionary history of its own; there is no reason to view it as a side-effect of some other adaptation.


8. It is advantageous for the members of a group to be able to communicate with each other. To facilitate communication, humans use what Caporael calls "unsituated coordination" or "shared construction of reality." The members of a band share particular ways of interpreting and evaluating events, and when they converse they talk about interpretations and evaluations, not about raw sensory data (if there is such a thing). That people do this is not a new idea; it is a basic tenet of sociology. The notion that, as a consequence, there will sometimes be "tensions" between the group's view of reality and an individual's experiences (a prediction Caporael makes in her abstract) has also been around for a while. Asch (1956) gave us a demonstration of that tension 40 years ago, when he described the discomfort of the subjects in his experiments on group conformity. The point of those experiments was not to show that people cave in to group pressure (not all of them did cave in) -- it was to show how surprised and troubled people are when their own perceptions fail to agree with the group's shared construction of reality.


9. Caporael is critical of all attempts to distinguish between the effects of heredity and environment. In repeated assemblies, genes are important only at the cellular level; those interested in human behavior should concern themselves with "functional relations between entity and environment, rather than just traits of the organism" (para. 8).

10. We are advised to stop studying human traits because (a) a trait such as nearsightedness can be compensated for by an artifact such as eyeglasses; and (b) an individual who exhibits a personality trait in one context may not exhibit it in another. The first of these statements seems to say that, because modern technology (eyeglasses) can wipe out some of the differences among us, there is no point in studying these differences. The second implies that the differences are not real because they are context-specific. The context-specificity of personality traits is a matter that personality theorists have been arguing about for decades (see Carson, 1989). Since the bathwater is by now very dirty, Caporael proposes throwing it out, and the baby along with it. I believe the baby is salvageable: human behavior is indeed context-specific, and yet humans are born with characteristics that they carry around from one context to another (Harris, 1995). It is true that the same individual behaves differently in different social contexts, but it is also true that, in the SAME social context, different individuals behave differently.

11. Even within a group, even when group identity is salient, different individuals behave differently. Caporael's theory focuses on the assembly process and ignores the entities that are being assembled. Not enough attention is paid to individual differences, or to the fact that group membership involves differentiation as well as assimilation. Over time, the members of groups adopt their own specialties, carve out their own niches, and typecast each other in different ways. These processes can lead to the exaggeration of individual differences.

12. The failure to acknowledge individual differences is quite evident in Caporael's blithe dismissal of the field of behavioral genetics: "Phenotypic features are fully codetermined by genes and environment in development throughout the lifespan . . . the phenotype cannot be analyzed into separate genetically determined and environmentally determined components" (para. 16). "It makes little sense to separate language into an innate and an acquired component; both are part of inherited resources" (para. 17). The first statement, that the phenotype cannot be analyzed into separate components, is inaccurate. Identical twins have exactly the same genes; therefore any phenotypic differences between them must be due entirely to environmental influences. The second statement, that it "makes little sense" to try to do this, betrays Caporael's nomothetic bias. Nomothetic approaches strive for general laws that are assumed to apply to "all of the people all of the time" (Scarr, 1992); human variability is regarded simply as noise. Behavioral genetics, in contrast, is an idiographic approach: it focuses on the variability and tries to explain why individuals differ from one another. In evolutionary psychology, theorizing tends to be of the nomothetic sort. This is ironic, because evolution itself would be impossible were it not for individual differences.

13. Ideally, a theory should be able to do both jobs at once: account for individual differences and posit general laws that apply to all humans. Efforts are currently being made to construct such theories -- see, for example, Scarr (1992) and Harris (1995) -- by combining the insights of evolutionary psychology with the findings of behavioral genetics. Behavioral genetics has produced at least one noteworthy and reliable finding in the past 15 years: growing up in the same home does not make siblings more alike in personality -- any similarity between them is due to shared genes, not to shared environment (Plomin & Daniels, 1987). This finding goes against commonly held assumptions and suggests that Caporael should not be so quick to conclude that parents' attitudes toward sex roles, or their use of artifacts such as cups with weighted bottoms, have important effects on children.

14. Ideally, a theory should also be testable. Although Caporael states that her article presents "a thesis to test" (para. 49), most of the statements in it do not seem to me to be open to disproof. She implies that her theory can be used "to derive testable, nonobvious hypotheses about human mental systems" (para. 3). Perhaps we would have a better grasp of what Caporael is getting at if she would derive some of these testable hypotheses for us.


Asch, S.E. (1956) Studies of independence and conformity: A minority of one against a unanimous majority. Psychological Monographs 70 (9, Whole No. 416).

Brewer, M.B. & Caporael, L.R. (1990) Selfish genes versus selfish people: Sociobiology as origin myth. Motivation and Emotion 14: 237-242.

Caporael, L.R. (1995) Sociality: Coordinating bodies, minds, and groups. PSYCOLOQUY 6(1) group-selection.1.caporael.

Caporael, L.R., Dawes, R.M., Orbell, J.M., & van de Kragt, A.J.C. (1989) Selfishness examined: Cooperation in the absence of egoistic incentives. Behavioral and Brain Sciences 12: 683-739.

Carson, R.C. (1989) Personality. Annual Review of Psychology 40: 227-248.

Harris, J.R. (1995) Where is the child's environment? A group socialization theory of development. Psychological Review 102: 458-489.

Plomin, R. & Daniels, D. (1987) Why are children in the same family so different from one another? Behavioral and Brain Sciences, 10, 1-60.

Scarr, S. (1992) Developmental theories for the 1990s: Development and individual differences. Child Development 63: 1-19.

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