From Mating to Mentality

Evaluating Evolutionary Psychology

Kim Sterelny, Julie Fitness

• Publisher: Psychology Press
• Year: 2004
• ISBN:
  9781135432126
• Edition: 1
• Topic: Psychologie
• Subtopic: Histoire et théorie en psychologie

Covering a range of topics, from the evolution of language, theory of mind, and the mentality of apes, through to psychological disorders, human mating strategies and relationship processes, this volume makes a timely and significant contribution to what is fast becoming one of the most prominent and fruitful approaches to understanding the nature and psychology of the human mind.

1

Introduction

The Evolution of
Evolutionary Psychology

KIM STERELNY
JULIE FITNESS

THE ADAPTED MIND PROGRAM

The publication of The Adopted Mind saw the canonical formulation of an important version of evolutionary psychology (Barkow, Cosmides, & Tooby, 1992). This collection both articulated and instantiated a very bold program for integrating evolutionary theory with cognitive psychology; an integration free of the defects of previous attempts to create an evolutionary theory of human nature. In comparison with its predecessors—especially Wilsonian sociobiology and its relatives—the Adapted Mind program had many attractions. In particular, see the following points.

The aim of this program was to identify and explain the computational mechanisms of the mind. Its focus was on the cognitive devices that generate behavior, not patterns in human behavior themselves; thus, this program shared the same explanatory focus and explanatory tools as contemporary cognitive psychology. Moreover, the adopted paradigm of the Adapted Mind adherents was chomskian linguistics. Over the last 40 years or more, Chomsky and his coworkers have developed a theory of language that is: (a) nativist, emphasizing our innate endowment for language acquisition; (b) cognitivist, in that the task is to specify the information possessed by Speakers about their native language rather than to predict actual linguistic behavior; and (c) domain-specific, in that the cognitive mechanisms that explain our core linguistic abilities are used only for language.

This paradigm has been enormously influential in cognitive psychology: modular, nativist theories of (for example) the child's theory of mind (Baron-Cohen, 1995; Leslie, 1994; Leslie & German, 1995) or of folk biology (Atran, 1998) are applications of Chomsky's picture in new domains. And despite Chomsky's own lack of interest in evolutionary questions, this picture dominates the Adapted Mind program too. Adapted Mind evolutionary psychologists ask different questions about our cognitive equipment, and use different heuristics to identify telling experiments. They aim to explain why we have the proximate mechanisms we do, and they exploit the evolutionary scenarios they construct to guide their experimental program. But they share with orthodox cognitive psychologists the conviction that the apparatus of the mind consists of domain-specific computational tools. This agreement about the fundamental mechanisms of the mind makes an evolutionary cognitive psychology possible.

Its defenders argue that the focus of the Adapted Mind program on cognitive mechanism brings with it a second advantage: testability. Specifically, Adapted Mind hypotheses (the idea goes) can be tested by the techniques of experimental psychology. For example, Cosmides and Tooby confirmed their hypothesis that we have domain-specific specializations for social exchange (they argued) by showing that we have differential inferential abilities. We reason better about social exchange contexts than others, for we have special adaptations for such domains (Cosmides, 1989; Cosmides & Tooby, 1989, 1992).

In contrast, Wilsonian conjectures are outrageously information-hungry. Consider, for example, one of the most provocative conjectures to emerge from the Wilson program: Thornhill's conjecture that rape is a facultative adaptation to sexual exclusion (Thornhill & Thornhill, 1987). To confirm this hypothesis, we would need to measure the fitness effect of rape on rapists, and because the offspring of an act of rape may be themselves doomed to low fitness, that entails measuring that fitness in the second generation. We would have to count rapists' grandchildren, and then compare that count with a population of nonrapists matched for their other relevant characteristics. And it gets worse, because we would have to project these fitness effects back in time. This is because the claim that rape is an adaptation is a claim about the evolutionary history of that behavior; its effect in ancestral populations on the fitness of males with the facultative propensity vis-à-vis those that lacked it. Moreover, we would need to show that the propensity is heritable. Therefore, even if the conjecture were right, assembling the evidence needed to confirm it would be virtually impossible. In short, Wilsonian conjectures are intrinsically difficult, perhaps impossible, to confirm. If it is really true that Adapted Mind conjectures can be tested by the methods of experimental psychology, then this is an enormous advance over its predecessor.

The Adapted Mind program is nativist, but it avoids all hint of genetic determinism by emphasizing the role of conditional strategies and by underlining the role of the environment in setting the parameters for innately structured modules. In its emphasis on the universality of human cognitive design, intentionally or not, the Adapted Mind program has avoided some of the political mud that stuck to Wilson and to those interested in the phenotypic effects of genetic Variation in human populations. Whatever its other failings, no one can claim the Adapted Mind program is racist.

EVIDENTIAL ISSUES

It is thus by no means surprising that over the last decade the Adapted Mind conception of the mind as an ensemble of adapted, innately specified, domain-specific, computational Subsystems has set the agenda for integrating psychology and evolutionary theory. This picture is compelling and bold. But, most important of all, is it really empirically tractable? Because historical processes destroy evidence about their own dynamic, testability is a perennial problem for any theory seeking to reconstruct evolutionary history. For example, the morphological trajectory that links the last common ancestor of humans and chimps is only partially preserved.

Moreover, information about the selective environments that drove those changes is both patchy and difficult to interpret. We do have increasingly well-documented evidence about the physical habitat of hominid evolution: landscape, climate, Vegetation, and ecology. But to a very considerable extent hominids construct their own selective environment (Odling-Smee, 1994; Odling-Smee et al., 2003; Sterelny, 2003). The size of hominid groups; whether they were sedentary or nomadic; their mating and child care practices; the extent of lethal intergroup conflict; the extent to which group life was cooperative (e.g., in supporting sick or injured members) are all factors that profoundly influence fitness and hence hominid evolutionary trajectories. Yet sociocultural Organization is hard to read off pollen counts and handaxe abrasion patterns.

The tendency of hominids to modify their selective environments in ways that are invisible in the palaeoecological record is a problem equally for the explanation of morphological and cognitive evolutionary trajectories. We cannot fully explain those trajectories if critical features of the selective environment have left no trace. However, the problem of identifying the trajectory to be explained is far more challenging for cognitive evolution. We now have a fairly good picture of the broad outline of morphological change in the hominid lineage over the last 3 million years (Klein, 1999). That is not true of the evolution of cognition. We cannot put firm dates to the first appearance of language; to the evolution of teaching and imitation learning; or to the formation of enduring pair bonds and paternal investment. Thus, the trajectory through which human cognitive capacities were assembled must be reconstructed from the physical traces of the behaviors generated by ancient minds. However, we are three ways removed from those minds. We see, not the behaviors themselves, but only the physical products of those behaviors. Worse: We see only a sample of those physical products. Moreover, the sample that survives is further modified; we get nothing in mint condition.

Our task, then, is to infer the nature of ancient minds from a small sample of their decayed products. This might seem a difficult ask, especially when we recall how controversial the hypotheses of cognitive psychology often are, despite unobstructed experimental access to subjects' actions, and the opportunity to experimentally intervene, prompting action of special interest in controlled circumstances. Cognitive psychologists are not doomed to passively observe the actions that happen to emerge from the cognitive stew of the agent. Even so, they argue.

These considerations are not meant to suggest that palaeontology is valueless; far from it. Indeed, two chapters in this volume (Corballis & Brockway) make pretty serious attempts to grapple with the trajectory problem for key human cognitive capacities (language and theory of mind). These considerations give us cause to squeeze as much information as possible out of Irving humans and their relatives. This brings us to perhaps the prime experimental showcase of the Adapted Mind program; the Wason selection task. In its original form, the Wason selection test presents subjects with a rule and a set of potential tests of that rule. One version might go like this. The subject is presented with the rule “If there is a square on the left side of the card, there is an even number on the right side” and four cards, each of which is half masked and half visible. The subject can see the left side of two of the cards. Of these, one shows a Square, the other a circle; the right-hand side is masked. The other two cards have their left side masked, and on the right are the numbers 8 and 11. Subjects are asked what cards they must see in order to test the rule. Subjects do very badly. Yet Cosmides and Tooby were able to show that if subjects are given a logically equivalent test about social monitoring and norm enforcement, they do much better. If subjects are asked which of these individuals they should check:

Sue is 16 and is drinking what?
Kate is 20 and is drinking what?
Samantha is drinking a Coke and is how old?
Louise is drinking a margarita and is how old?

and if the rule to be tested is: “If you are drinking alcohol, you must be over 18,” they do fine.

They used this experimental finding as a key part of their argument for a social exchange module. This seems like a very impressive case for the Adapted Mind program. First, this is a surprising datum: in contrast (perhaps) to some of the results about human mating preferences, no one can accuse Cosmides and Tooby here of just dressing folk prejudice in Darwinian clothes. Second, it seems very elegantly explained by the idea that the mind is a set of domain-specific modules, because that hypothesis predicts that our cognitive Performance will be highly variable across logically equivalent problems. Thus, it seems quite reasonable to argue that these results provide some support, not just for the claim that our reasoning capacities are content sensitive, but also for the evolutionary scenario that promoted the Cosmides-Tooby experiment. Specifically, they argued as follows: We evolved in social environments in which Cooperation and exchange were essential to survival, but where free riding was a threat. We would have been under selection to cooperate; to trade, but warily. The unconditionally trusting would not have done well, but nor would those who did not trade at all. We should be adapted to reason well about social exchange; in particular, we should be alert to free riders and their ilk.

This scenario is the best explanation of the Wason selection phenomenon, and hence is confirmed by that phenomenon. That confirmation, of course, would be strengthened by parallel cases. In particular, we should look to other inferential tasks to see whether we observe the same patchy performance, but with improved Performances showing up on problems about the same topics. For example, we are notoriously fallible probabilistic reasoners, being subject to a variety of gambler's fallacies and the like. The Adapted Mind case for a domain-specific adaptation is strengthened to the extent that other tendencies to poor reasoning disappear when reasoning about policing social exchange.

In the language of philosophy of science, then, the Adapted Mind inference from domain-specific reasoning skills to the confirmation of an adaptationist hypothesis about those skills is an “inference to the best explanation.” Such inferences are tested by attempting to develop alternative explanations, and the chapters in this volume by Sperber and Gray exemplify this strategy. These authors argue that, as it stands, this experimental program does not reveal the existence of domain-specific reasoning skills, because there are alternative explanations of elevated performance on the Wason test. In particular, they argue that a number of relevance heuristics make the possibility of cheating especially salient in the “rule violation” versions of these tests but not in the neutral controls. The ability to use these heuristics is itself quite likely to be an adaptation, but it is a much broader spectrum one than one specifically designed to monitor social exchange. Accordingly, there is no adaptationist inference to the best explanation of these reasoning skills.

THE SHADOW OF THE PLEISTOCENE

The chapters in this volume also signal a rapprochement between evolutionary psychology and human behavioural ecology. Around the time the Adapted Mind program was developing, there was a vigorous exchange of views about adaptive behavior (especially in a special issue of volume 11 of Ethology and Sociobiology). The Adapted Mind program has no special interest in the extent to which contemporary humans act adaptively. Human cognitive machinery (their idea goes) evolved in the ecological and social world of Pleistocene hunting and gathering. None of us now live in the Pleistocene, and very few of us live in hunter-gatherer social worlds of any kind. Thus, measuring (say) the birth spacing of Polynesian women in the Cook Islands would test no evolutionary hypothesis. Suppose, for example, we were to discover that their birth spacing is adaptive, tending to optimize the expected number of their grandchildren by approximating the right trade-off between the number of children and the investment per child. So what? We have no idea, from that, what spacing pattern the proximate mechanisms that determine birth spacing decisions would deliver in the very different environment of the Pleistocene. Still less do we know whether that pattern would be adaptive in that environment. Adaptations to past environments might well drive actions that are now maladaptive as a result of environmental change. Fondness for sugar and fat are favorite examples, but Siegert's chapter is a much more ambitious example of this genre. Indeed, it is largely concerned with this possibility: He explores the hypothesis that psychological disorders (in particular, depression) are the result of cognitive mechanisms misfiring maladaptively because of a mismatch between current and ancestral environments. Moreover, currently adaptive behaviors can have similar explanations: Adaptations to past environments might generate fortuitously adaptive behavior in response to evolutionarily novel phenomena. According to this perspective, only the past explains the present.

In contrast, anthropologists with evolutionary interests (dating from Alexander and Chagnon) have always been interested in the extent to which the behaviors of contemporary humans are adaptive (Betzig, 1999). Those anthropologists have not developed very explicit models of human cognitive capacities. But their working assumption has been that human capacities to respond adaptively across a wide range of social and physical environments are not sharply constrained by innate constraints on our reasoning and motivation Systems. Thus, they expect to find humans responding adaptively to many of the challenges they face. Moreover, they expect those findings to be evolutionarily significant, although, not, of course, in the sense that current patterns of action explain existing cognitive mechanisms. Rather, they expect contemporary behaviors—and especially the spread of adaptive responses in a range of different social environments—give us a good guide to the fitness challenges faced by our ancestors and how those challenges were met. According to this perspective, then, the present is a guide to the past (Downes, 2001; Irons, 1999; Smith & Borgerhoff Mulder, 2001).

This volume sees that gap between these two views narrowly dramatically. In particular, the chapters by Simpson and Oriña, Fletcher and Stenswick, and Kenrick et al. (all on aspects of mate choice) signal a move to synthesize these once competing alternatives. They contrast with earlier versions of evolutionary anthropology in developing explicit hypotheses about the cognitive mechanisms involved in mate choice and relationship maintenance. But they also accord with evolutionary anthropology in emphasising the multiplicity of human mating strategies—in particular, the extent of intrasexual variability—and the extent to which different individuals acting within the constraints of their actual situations succeed in acting adaptively.

For example, Simpson and Oriña see women's sexual strategy as dominated by the trade-off between seeking good genetic resources and economic investment from their mates. Male strategies make it difficult in general for women to optimize both types of resource at once; therefore, often one trades off against the other, with the appropriate trade-off being very sensitive both to environmental factors and to women's specific circumstances. Moreover, their data suggest that women make these trade-offs astutely and adaptively. To the degree that they make predictions about the extent to which agents act adaptively (and the chapters vary somewhat in this), these theorists increase the empirical content of their hypotheses.

Our guess is that it is no accident that mate choice is the leading edge of this synthesis; it is most unlikely that mate choice in the Pleistocene was simple. Thus, we are not surprised by Gray's data suggesting that male attractiveness judgments, including the response to waist-to-hip ratios, are developmentally plastic rather than being wired in. In contemporary hunter-gatherer societies, such choices are constrained and complicated by idiosyncratic features of the group's culture (e.g., their outbreeding rules); the extent to which ind...

Table of contents

• Front Cover
• Half Title
• Macquarie Monographs in Cognitive Science
• Title Page
• Copyright
• Contents
• About the Editors
• Contributors
• Preface
• 1 Introduction: The Evolution of Evolutionary Psychology
• 2 Evolutionary Cognitive Science: Adding What and Why to How the Mind Works
• 3 Strategic Pluralism and Context-Specific Mate Preferences in Humans
• 4 The Intimate Relationship Mind
• 5 Evolving to Be Mentalists: The “Mind-Reading Mums” Hypothesis
• 6 Uncertainty, Contingency, and Attachment: A Life History Theory of Theory of Mind
• 7 Recursion as the Key to the Human Mind
• 8 Reinterpreting the Mentality of Apes
• 9 Does the Selection Task Detect Cheater-Detection?
• 10 Clinical Psychology and Evolutionary Psychology: Strange Bedfellows?
• 11 Evolutionary Psychology and the Challenge of Adaptive Explanation
• Author Index
• Subject Index