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Evolutionary Psychology

Evolutionary Psychology

BIBLIOGRAPHY

Evolutionary psychology proposes a set of evolved psychological mechanisms to account for much, if not all, human behavior. The research program is one among many in the social sciences that argues for the relevance of evolutionary biology in understanding human behavior. Evolutionary psychologists argue that explanations in psychology, and social science in general, are inadequate to the extent that they ignore human evolution. Evolutionary psychologists aim to unify psychology and other social sciences and improve their explanatory capabilities. Evolutionary psychology is related to human sociobiology but evolutionary psychologists present an important criticism of human sociobiology: sociobiologists ignore the psychological mechanisms that produce human behavior. To this extent, evolutionary psychology is seen as an advance over human sociobiology because it is consistent with cognitivism in psychology. Evolutionary psychologists share cognitive psychologists view that humans internal psychological mechanisms are contentful representational states, sometimes referring to these mechanisms as Darwinian algorithms. Behavioral psychologists argue that humans have no content internal representational states, which is in stark contrast to the cognitive perspective.

Evolutionary psychologists key contribution to the social sciences is the idea that the human mind consists of many separate psychological mechanisms, each of which was formed by natural selection. An analogy with organs illustrates this key insight: Many human organs are adaptationsdirect descendents of organs that helped our ancestors survive and reproduce. Keeping with the analogy, these researchers point out that although all psychological mechanisms are adaptations, they need not all be currently adaptive, just as humans appendices are adaptations but are not currently adaptive. Similar to human organs, the relevant adapted mental mechanisms are distinct and evolved independently of one another; they are modular.

A large number of experimental projects gave weight to evolutionary psychologists theoretical claims. Psychologist David Busss 1990 study of human mate selection found large numbers of cross-cultural commonalities in mate choices. These commonalities were attributed to various underlying psychological adaptations that drive human mate choices. Leda Cosmidess work during the 1980s in the psychology of reasoning presented a new way of dealing with a type of reasoning puzzle called Wason selection task results. Wason selection tasks are presented in the context of psychological experimentation on human reasoning. In the earliest of these, test subjects were presented with abstract tasks that could be solved correctly by use of deductive logic. Most subjects fail to deal with such tasks correctly and subsequent researchers introduced versions of the tasks with the same logical structure but presented in a context that subjects understood. These versions of the task produced a huge improvement in performance. Much of the psychology of reasoning has focused on explaining this performance difference. Cosmides proposed that performance goes up on Wason selection tasks when they are construed in terms of social exchange because humans are deploying an evolved psychological mechanism for social exchange to carry out the selection task.

Other experimental results reported by evolutionary psychologists include controversial work on rape and murder, as well as work on many aspects of reasoning, moral judgment, sexual attractiveness, parenting, taste, aggression, cooperation, and mental health. The Handbook of Evolutionary Psychology details the theoretical underpinnings of the field and introduces many of the key results from empirical work. This book develops and advances upon the program announced in an earlier work, The Adapted Mind.

Evolutionary psychology is an extremely productive research program. Evolutionary psychologists produce a large body of both academic and popular work. This work simultaneously advances a research program and provides responses to the various critics of the program. The first broad type of criticism is mounted by social scientists who view evolutionary psychology as a kind of biological determinism. Evolutionary psychologists reply that neither biological determinism nor cultural determinism is a viable explanatory strategy in the social sciences if pursued exclusively. Critics respond that the reductionist goals of evolutionary psychology imply that they are not as ecumenical as their response would indicate.

There are two other types of criticism of evolutionary psychology. One critique comes from researchers in other biologically based social sciences, such as evolutionary anthropology, who argue that evolutionary psychologists presuppositions about human evolution are mistaken and that their hypotheses are not subjected to the testing procedure that analogous hypotheses undergo in evolutionary biology. This debate is about how to develop and test hypotheses about adaptation. Much of this discussion has centered on the issue of whether to test for adaptive behavior or to attempt to ascertain whether a certain behavior is the result of a particular adaptation. Evolutionary anthropologists adopt their methodology from behavioral ecologists. This approach emphasizes producing models to test the extent that animal or human behavior is adaptive. Evolutionary psychologists argue that ascertaining whether or not a trait is currently adaptive for the animal or human is not the same as ascertaining whether the trait is an adaptation or whether the behavior results from an adaptation. Evolutionary anthropologists counter the hypotheses that the extent to which behavior is adaptive can be rigorously tested and is relevant with the question of whether or not behavior is an adaptation or results from an adaptation.

The other type of criticism comes from philosophers of science, who place almost every aspect of the research program under critical scrutiny. Such critics reject both the theoretical tenets of the program, such as the modularity assumption, and the viability of experimental results.

Many philosophers of science, including philosopher of biology David Buller, have argued that evolutionary psychologists are mistaken in claiming that human minds are massively modular. Such arguments are derived from work in biology and from alternate views about human mental architecture defended in the cognitive sciences and neurosciences. Philosophers also argue that evolutionary psychologists are committed to an untenable version of adaptationism. Bullers version of this latter criticism is developed along similar lines to the criticisms presented by evolutionary anthropologists. One idea here is that not all adaptationist hypotheses should be considered equal and only those that are susceptible to rigorous empirical test should be pursued. Philosophers present another version of this point arguing that evolutionary psychologists version of adaptationism is not consistent with evolutionary biologists adaptationism and is therefore suspect. It is important to emphasize that critics from evolutionary anthropology and philosophy of science share evolutionary psychologists view that evolutionary biology is crucial in the overall project of understanding human behavior. The critics disagree with evolutionary psychologists about the way in which biology should be brought to bear in the study of human behavior.

There is broad agreement among some social scientists that much of human behavior will only satisfactorily be accounted for by using biological based explanatory models. Such agreement does not commit these researchers to the view that evolutionary psychologists have isolated the one correct way in which biology should be brought into social science. There is still a great deal of theoretical and experimental work to be done at the intersection of biology and the social sciences. This is an exciting growth area to which evolutionary psychology makes one prominent contribution.

SEE ALSO Anthropology, Biological; Darwin, Charles; Natural Selection; Philosophy; Psychology; Social Science; Sociobiology

BIBLIOGRAPHY

Barkow, Jerome H., Leda Cosmides, and John Tobby, eds. 1992. The Adapted Mind: Evolutionary Psychology and the Generation of Culture. New York: Oxford University Press.

Buller, David. 2005. Adapting Minds: Evolutionary Psychology and the Persistent Quest for Human Nature. Cambridge, MA: MIT Press.

Buss, David M., ed. 2005. The Handbook of Evolutionary Psychology. Hoboken, NJ: John Wiley & Sons.

Buss, David M. 2005. The Murderer Next Door: Why the Mind Is Designed to Kill. New York: Penguin.

Buss, David M., Max Abbott, and Alois Angleitner, et al. 1990. International Preferences in Selecting Mates: A Study of 37 Cultures. Journal of Cross Cultural Psychology 21: 547.

Cosmides, Leda. 1989. The Logic of Social Exchange: Has Natural Selection Shaped How Humans Reason? Studies with the Wason Selection Task. Cognition 31: 187276.

Hrdy, Sarah B. 1999. Mother Nature: Maternal Instincts and How They Shape the Human Species. New York: Ballantine Books.

Pinker, Steven. 2002. The Blank Slate: The Modern Denial of Human Nature. New York: Viking.

Wason, Peter C. 1960. On the Failure to Eliminate Hypotheses in a Conceptual Task. Quarterly Journal of Experimental Psychology 12: 129140.

Stephen M. Downes

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Evolutionary Psychology

Evolutionary Psychology


Evolutionary psychology assumes that operating beneath the surface of historical and cultural variability, the human mind is a system of functionally specialized, developmentally constructed neural information processors that were naturally selected because they solved particular adaptive problems faced during the evolution of the hunter-gatherer ancestors of human beings. Evolutionary psychology assumes a computational theory of mind rooted in the information processing revolution of the 1960s. It also draws on insights from the socio-biology of the 1970s, which describes how "selfish" genes, in benefiting their own replication and that of copies amongst kin (William D. Hamilton's "inclusive fitness"), direct the generation of organic structures, including those that may incidentally benefit the organism. With the natural selection of species-wide characteristics, evolutionary psychology considers sexual selection, including the effects of parental investment, and has made empirical contributions to understanding the proximal mechanisms behind mate choice, cheater detection, and language acquisition.

Evolutionary psychology avoids a collapse to genetic determinism through its attention to development and environment, including social interaction and coevolutionary systems. Nevertheless, any computational theory of mind may ultimately be inadequate, and there are questions about the empirical robustness of its findings.


See also Evolutionary Epistemology; Evolutionary Ethics; Selfish Gene; Sociobiology

Bibliography

hamilton, william d. "the genetic evolution of social behavior." journal of theoretical biology 7 (1964): 1718.

pinker, steven. how the mind works. new york: norton, 1997.

wright, robert. the moral animal: the new science of evolutionary psychology. new york: pantheon, 1994.

john a. teske

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Evolutionary Psychology

EVOLUTIONARY PSYCHOLOGY

Human beings are evolved creatures. Our lineage stretches back through the first humans to have evolved roughly 150,000 years ago, through their hominid ancestors, all the way back to the common ancestor we share with all other forms of life on the planet. Many of our traits are the historical results of evolution. This holds as much for psychological traits such as the visual system, emotions, and some behavior-producing mechanisms as for physical traits such as the heart, eye, or hand.

In a broad sense, evolutionary psychology covers any inquiry that uses this fact about our biological heritage to illuminate our human psychology. Historically, Charles Darwin himself pursued this kind of inquiry, as did such disparate figures as Herbert Spencer, John Dewey, and Sigmund Freud. Contemporary scientific fields such as human ethology and evolutionary anthropology are also instances of evolutionary psychology in the broad sense.

More commonly, however, the term evolutionary psychology is used in a narrower sense to refer to a specific research program that deserves to be called a Kuhnian paradigm. This paradigm is most closely associated with the psychologist Leda Cosmides (1957) and anthropologist John Tooby, who have been among its strongest and most vocal advocates; other prominent figures in this paradigm include David Buss (1953), Martin Daly (1944), Steven Pinker (1954), Donald Symons (1942), and Margo Wilson (1942). The manifesto for this group is the 1992 volume The Adapted Mind. This specific paradigm has been the most controversial branch of the general evolutionary approach to psychology and is therefore the focus of this entry. Unless otherwise qualified, evolutionary psychology will here be used to refer to this specific paradigm. There are four distinctive theoretical commitments in this paradigm of evolutionary psychology.

Computationalism

In keeping with most cognitive science and much contemporary psychology, evolutionary psychology construes the mind as an information-processing machine, which can be described in cognitive and computational terms. What is important about the mind is not what it is made of but what it does, namely, take in information from the environment, operate on internal representations, and produce behavior. The physical properties of the brain, such as its size and the amount of energy it requires, may have played some role in our evolution; but at least as important in evolution is what the mind does, and this is to be characterized functionally.

Adaptationism

Organisms possess many traits that appear to have been designed to help them survive and reproducephotosynthesis in plants, the vertebrate eye, and so on. Such traits increase the fitness of the organism, which essentially means they make it more likely for the organism to transmit its genes to future generations. These traits are adaptive.

Evolution by natural selection is the best explanation for the existence of complex and functionally integrated traits such as the eye. Natural selection works by preserving and modifying heritable mutations that increase their possessors' fitness. Suppose some organism is born with some novel and simple trait (due to random mutation) that gives it a slight fitness advantage over its conspecifics. The next generation will tend to have more such organisms, and so the new trait will spread throughout the population. The more common the trait becomes in the population, the more likely that some new, beneficial mutation will arise in organisms with that trait, in which case organisms with both mutations will become more frequent in the population, and so on. By accumulating many small, beneficial mutations, natural selection can build complex and well-designed traits. Traits that evolved because they increased their bearers' fitness are adaptations.

Two questions can be distinguished about any trait: first, whether it is an adaptation and, second, whether it is currently adaptive. The first is an historical question concerning the role of natural selection in the origin of the trait; the second concerns whether the trait at the present time fits the organism to its environment (strictly, whether the trait tends to increase the organism's genetic representation in later generations). Adaptations must have been adaptive when they evolved, but they need not be adaptive now. They may no longer fit the environment if it differs from the environment in which the trait evolved.

Evolutionary psychologists claim that the human mind contains many traits that are adaptations (but may no longer be adaptive in modern environments). The environment in which traits evolved is called the environment of evolutionary adaptedness (EEA). Note that environment is construed broadly in evolutionary theory, covering geographical, physical, biological, and social factors. In the case of human psychological evolution, the social environment must have been especially important. According to evolutionary psychologists, the human EEA was the Pleistocene era, which started about 1.8 million years ago and ended 10,000 years ago. They argue that there has not been enough time since then for selection to have produced any significant new adaptations. Adaptations take time to evolve, especially such complex adaptations as psychological traits, and there have not been enough generations since the Pleistocene for new psychological adaptations to evolve.

Throughout the Pleistocene, human beings lived as hunter-gatherers in small-scale groups. Hence our adaptations are equipped to deal with this kind of environment but not necessarily modern environments, which are different in many salient ways. Our food preferences are a commonly cited psychological example. Humans enjoy and seek out foods high in sugar and fat. In the nutrient-poor environment of the Pleistocene, such preferences were adaptive since they helped our ancestors maximize their caloric intake. But they are no longer adaptive in modern environments in the developed world where such foods are all too readily available.

Since the mind/brain is an organ of tremendous complexity and sophistication, evolutionary psychologists argue that it must have evolved by natural selection. More than that, specific psychological mechanisms evolved to solve the suite of adaptive problems faced by our hunter-gatherer ancestorsproblems of how to increase their genetic representation in future generations. This fact is crucial to understanding the mind, claim evolutionary psychologists, because it allows researchers to engage in reverse engineering. In an evolutionary functional analysis, evolutionary psychologists try to infer what adaptive problems our ancestors would have faced and what sorts of psychological mechanisms would be required to solve them on the basis of what is known about conditions in the human EEA. Through such an analysis they generate hypotheses about our psychological adaptations and then test for the presence of these adaptations in modern humans.

Modularity

The third main theoretical commitment of evolutionary psychology follows naturally from the previous one. The mind is not a single, monolithic adaptation, argue evolutionary psychologists. Rather, the mind is comprised of many functionally distinct units dedicated to solving specific adaptive problems faced in the EEA. These distinct psychological mechanisms are modules.

When Jerry Fodor first developed the notion of a psychological module in The Modularity of Mind (1983), he characterized them as sharing a cluster of nine distinctive features. Evolutionary psychologists have focused on only a subset of these. The modules they propose are supposed to operate fast and automatically (without conscious effort). They are more or less informationally encapsulated from other psychological mechanismsthey do not have full access to all the information stored elsewhere in the mind. Finally, they possess innate information about the adaptive problem they were designed to solve.

Fodor himself believed that modules would only be found at the functional periphery of the mind, handling input processes such as vision. More controversially, evolutionary psychologists claim not only that more central cognitive processes are modular but also that the mind is massively modular. Cosmides and Tooby (1992), for instance, claim that the mind must contain thousands of different modules, each of them dedicated to solving different adaptive problems (and subproblems) in the EEA.

Evolutionary psychologists have offered some general evolutionary arguments for why the mind should be largely comprised of modules rather than domain-general processes. First, the adaptive problems our ancestors faced were many and variedforaging for food, selecting the best possible mate, avoiding incest with one's kin, and so onand these require different sorts of solutions. A mind with domain-specific ways to solve these problems is faster, more efficient, and more reliable than a general-reasoning sort of mind. Therefore, modular minds would have been selected over general reasoners in our ancestral lineage, and our own evolved cognitive architecture should be massively modular.

The second argument for massive modularity is that only massively modular minds could have produced adaptive behavior. General reasoners could not have learned by themselves and in their own lifetimes the advantages of avoiding incest or helping kin, especially since what counts as error and success is not the same in all domains. Modular creatures with domain-specific knowledge of what to do and when to do it would have been fitter than general reasoners.

Universality

The last main theoretical commitment of evolutionary psychology is that psychological adaptations are part of our universal human nature, with two exceptions: where a person lacks the adaptation because of mutation, and some cases of sex differences (in particular, adaptations concerning sexual reproduction). Evolutionary psychologists believe this about adaptations in general: Any trait that increases its bearer's fitness will tend to spread to fixation through a population, given enough time. Since our psychological adaptations evolved during the Pleistocene, there was enough time for them to become fixed in the entire human species.

Evolutionary psychologists have several defenses against the obvious rebuttal that human psychological nature looks anything but universal. First, they tend to downplay the massive cultural differences that anthropologists in the early to mid-twentieth century claimed to have found. Second, and a less ad hoc defense, evolutionary psychologists claim only that our psychological adaptations are universal, not that all our psychological traits are universal. Given that they also view complexity as the mark of an adaptation, however, this concession does not really grant the possibility of variation in complex psychological traits.

Their third, most interesting defense is that, even if we grant significant diversity across and between cultures, this diversity may still be produced by a common underlying mechanism. Evolutionary psychologists are interested not in behavior but in the psychological adaptations that produce behavior. An adaptation exposed to one set of environmental cues might produce a different behavior if it were exposed to a different set of cues.

One way a universal mechanism can produce diversity is a common psychological mechanism responding differently to different environmental cues. The linguistic work of Noam Chomsky, himself not an evolutionary psychologist, provides a classic example of this. According to the Chomskian tradition, the world's various languages are all underwritten by a basic universal grammar. All normal humans possess a modular language-acquisition device that enables us to learn the language of our native environment during a certain critical period of development. Although two humans may speak two different languages, they acquired, comprehend, and speak their own language with the same mechanisms.

A second way to get diversity from a universal mechanism is where a common developmental program produces different psychological mechanisms in different environments. For instance, some mechanisms may only develop in the presence of certain environmental cues at certain stages of development. In environments where those cues are lacking, or where different cues are present, the mechanism will not develop. Evolutionary psychologists have proposed both types of explanation of how an underlying common human nature can produce behavioral diversity.

Strictly speaking, then, when evolutionary psychologists claim that our evolved psychology is universal, they mean this in a restricted sense. It is not behaviors, beliefs, or desires that are supposed to be universal but only our psychological adaptations. In some cases even the psychological mechanisms themselves are not universal but only the developmental programs that produce those mechanisms in the appropriate environments.

Specific Adaptations Proposed by Evolutionary Psychologists

Evolutionary psychologists have proposed too many psychological adaptations to list here, but two examples should suffice. Cosmides and Tooby (in "Cognitive Adaptations for Social Exchange") proposed a module dedicated to detecting cheaters in social exchanges. This module was postulated to explain a puzzling pattern of results on the Wason selection taska psychological test. Humans tend to perform very badly on this task when it is framed as an abstract logical problem but perform much better when it is framed as a problem for detecting potential social violations. According to Cosmides and Tooby, we should predict that humans have a dedicated cheater-detection module because detecting cheats was a serious adaptive problem for our ancestors in the EEA, and this module is invoked by the second but not the first frame in the Wason task.

The second example of a proposed psychological adaptation is even better known and comes from Buss (particularly in The Evolution of Desire ). According to Buss, different reproductive strategies would have been successful for men and women in the EEA, and so men and women should have evolved different mating preferences. Men who preferred to mate with younger, more fertile women would have been more reproductively successful than other men. Conversely, women who preferred to mate with high-status men would have been more reproductively successful than other women. In a massive cross-cultural survey, Buss claimed to have shown that these preferences exist to this day.

Problems with Evolutionary Psychology

Evolutionary psychology has been the subject of much critical scrutiny, from philosophy, psychology, and evolutionary biology. Each of its four main theoretical commitments is contentious, and the empirical case for many of its substantive claims has also been contested.

problems with computationalism

It is worth noting briefly that computationalism does have some critics in philosophy of mind. Such critics will thus be skeptical of evolutionary psychology since it assumes that the mind is computational in nature (at least, the parts of the mind of interest to evolutionary psychology). Critics of evolutionary psychology, however, have not tended to challenge its computational assumptions since these are widely shared in cognitive science and contemporary philosophy of mind.

problems with adaptationism

Much more attention has been paid to the adaptationism of evolutionary psychology. Many biologists and philosophers of biology have looked upon adaptationist reasoning with suspicion since the biologists Stephen Jay Gould (19412002) and Richard Lewontin (1929) published their famous critique The Spandrels of San Marco and the Panglossian Paradigm. Gould and Lewontin charged that adaptationist hypotheses about ancestral conditions are too speculative, often little more than just-so storytelling. Moreover, the dogmatic assumption that every trait must be an adaptation exaggerates the power of selection to overcome constraints imposed by development and population size. Finally, adaptationism neglects the other ways a trait might have evolved, in particular, that a trait might have evolved for one purpose and only later been co-opted for its current use.

For their part, adaptationists have denied the charge of dogmatism; their assumption that any particular trait is an adaptation is a heuristic one, which produces hypotheses about ancestral adaptive problems. These adaptationist hypotheses should be seen as forms of argument to the best explanation and, where possible, can and should be tested against the available empirical evidence.

The appropriateness of adaptationist reasoning is still a much debated question in evolutionary biology. Regardless of the answer to that question, however, the critique of Gould and Lewontin cannot be directly applied to evolutionary psychology. Evolutionary psychologists expressly admit that the original adaptive problem cannot be inferred from the present adaptiveness of a trait. They accept the standard distinction between the historical origin of a trait as an adaptation and its present status as adaptive or otherwise, and they believe that many adaptations are no longer adaptive.

Moreover, the reasoning in evolutionary functional analysis goes in the opposite direction to standard adaptationist reasoning. Adaptationism typically starts with an identifiable biological trait and works backward to hypotheses about the ancestral adaptive problems. By contrast, evolutionary functional analysis starts with hypotheses about the ancestral adaptive problems and predicts traits that should have evolved to solve them. If these traits can then be found in modern populations, the successful prediction corroborates the hypothesis about ancestral conditions, and we have also made some new discoveries about modern psychology.

This last point, however, highlights a legitimate theoretical concern about the adaptationism of evolutionary psychology. For evolutionary functional analysis to succeed, hypotheses about ancestral conditions must meet two conditions: First, they must be sufficiently likely to be true (or else there is no point in testing predictions derived from them), and secondly, they must be detailed enough to suggest testable predictions.

Evolutionary psychologists can draw on three main sources of evidence when developing hypotheses about ancestral conditions: direct prehistorical evidence of actual conditions in the Pleistocene, the conditions faced by still-extant groups of hunter-gatherers, and our close relatives among the nonhuman primates (primarily the chimpanzee). There is some reason to doubt that any of these sources can provide good enough evidence to meet the two conditions just mentioned, for the prehistorical record is sparse, nonhuman primates have undergone their own evolutionary trajectories since they diverged from our common ancestor, and the lifestyles of extant hunter-gatherer populations have probably changed significantly since the Pleistocene. It is also debatable whether humans in general have stopped accumulating adaptations since the end of the Pleistocene, as evolutionary psychologists claim.

If these concerns are well placed, then our knowledge of ancestral adaptive problems is at too coarse a grain to entail detailed predictions about psychological mechanisms. Granted, we can be sure of very general statementsfor instance, that our ancestors faced the ancestral problem of securing a suitable matebut their very generality robs them of predictive power. All sexually reproducing organisms face this problem, and the adaptations they evolve to solve it vary dramatically. Such coarse adaptive problems cannot provide any predictions about specific psychological solutions in human beings.

Of course evolutionary psychologists deny that the limits to our knowledge of ancestral conditions are so great; hence, a main point of contention is how much skepticism is warranted by these limits. Evolutionary psychologists think it is still possible to produce sufficiently detailed hypotheses even with such limited evidence; their critics claim otherwise.

problems with modularity

As with adaptationism, the concept of modularity has been the subject of general controversy, this time in psychology. Since Fodor's 1983 book, the notion of a module has been highly influential in cognitive science and psychology. There is broad agreement on the existence of at least some modules, notably, modules for language and for visual processing. The disagreement is over the amount of modularity in the mind as a whole.

Fodor himself from the start denied that the mind could be modular, except at the periphery. He later expanded these arguments into an assault on massive modularity in The Mind Doesn't Work That Way. According to Fodor, a massively modular mind would not be able to entertain thoughts with contents that cross the domains of each moduleit would be epistemically bounded. For instance, if the mind contained separate modules for thinking about numbers, physical objects, other minds, and so on, it could not entertain a thought about both numbers and objects. A fortiori, it could not integrate information about these various domains in reasoning.

The human mind, however, does not appear to be epistemically bounded in this way, at least for central reasoning processes. Our mind is flexible in the sorts of thoughts it can entertain; moreover, it can use information from different domains flexibly in abduction. Suppose we are trying to predict the outcome of an upcoming election; potentially, information about almost anything might be relevantfacts about geography; meteorology; economics; psychology. Human minds seem able to integrate relevant information from any domain of thought.

At most, however, Fodor's arguments show only that the mind cannot be completely modular. There is need for some central workspace where information from the various modules can be integrated. But this does not show that even central processes might not be substantially modularized. In particular, it fails to show that the mind could not contain modules dedicated to solving specific adaptive problems as well as nonmodular components downstream.

A more pressing criticism is offered by Richard Samuels (in "Evolutionary Psychology and the Massive Modularity Hypothesis") against the evolutionary psychologists' arguments for massive modularity. Samuels distinguishes between two types of module: computational and Chomskian. Computational modules are, so to speak, distinct computers with their own proprietary mental programs. Chomskian modules, by contrast, are mentally represented bodies of innate, domain-specific information that are supposed to underlie our cognitive abilities in various domains. Crucially, Chomskian modules are not computationally isolated but, rather, merely separate databases of information about the world. Various psychologists have posited the existence of such innate knowledge for domains such as intuitive physics, numbers, intuitive psychology, and universal grammar.

Samuels claims that the arguments from evolutionary psychology show the need for some domain-specific knowledge of the sort contained in Chomskian modules. Perhaps organisms do need substantial amounts of knowledge about the adaptive problems their ancestors faced in order to succeed at reproduction. This does not support the existence of the separate computational modules posited by evolutionary psychologists. All this domain-specific knowledge may be operated on by the same domain-general cognitive processes. It is one thing to argue that the mind must have a vast library of domain-specific information; it is another thing to show that it must also have a vast network of different computers dedicated to using that information.

problems with universality

Finally, there is room for debate about the evolutionary psychologists' argument that adaptations will generally be universal. There are known evolutionary mechanisms that can maintain alternative traits in a population, in particular, frequency-dependent selection. Frequency-dependent selection occurs when there is a set of alternative traits, no single one of which is the fittest overall. Rather, the fitness of any one of these traits depends on which traits are present in other organisms in the population and at what frequency. In some cases frequency-dependent selection can maintain polymorphismthat is, the presence of more than one alternative trait in a populationat a stable ratio in which each trait has equal fitness.

Evolutionary psychologists deny that such mechanisms would have produced true genetic polymorphism in humans. Rather than, say, two different sets of genes that produce two alternative traits, there would be a single set of genes that could itself produce the alternative traits (either randomly or in response to environmental cues, where these are available). Selection will favor this kind of adaptive plasticity over polymorphism.

Evolutionary psychologists have not provided a very good argument for this. They claim that sexual reproduction would disrupt complex adaptations unless both partners shared genes for all the adaptive traits in the population. The chief problem with this argument is that it is too strong, for it would disprove the possibility of complex genetic polymorphisms in any sexually reproducing species. Since there are several cases of genetic polymorphisms in different species, the argument cannot be sound.

The Empirical case for Evolutionary Psychology

All these problems with the theoretical commitments of evolutionary psychology would mean little in the face of good empirical results. If evolutionary psychologists could point to universal psychological adaptations discovered by evolutionary functional analysis, the paradigm could be declared a success, regardless of any theoretical misgivings. Assessing the empirical case for particular evolutionary psychological claims is well beyond the scope of this entry; moreover, any such assessment would be out of date even before it went to print.

What can be said here is that the empirical case remains fiercely contested. Buss has put forth what evolutionary psychologists consider their textbook cases in his Evolutionary Psychology ; David Buller (1959) challenges the empirical case for three of these putative adaptations in Adapting Minds. The empirical terrain here is still up for grabs and will probably continue to be so for some time.

Conclusion

There are several reasons to be suspicious of the main theoretical commitments of the Cosmides and Tooby paradigm of evolutionary psychology. These reasons counsel caution about accepting uncritically the various empirical claims put forth by this paradigm. They do not prove that these claims are false, that they have not been adequately empirically supported, or that they will never be supported. To assess the claims of evolutionary psychology, our only recourse is to look to the data.

Finally, it must be stressed that the evolutionary psychology discussed here is only one paradigm within a broader field of inquiry that tries to integrate evolutionary and psychological research. Even if this specific paradigm is not entirely successful, this does not impugn the broader field itself. For human beings have evolved, and surely this fact should be relevant to psychology.

See also Chomsky, Noam; Computationalism; Darwin, Charles Robert; Darwinism; Dewey, John; Evolutionary Theory; Fodor, Jerry A.; Freud, Sigmund; Philosophy of Mind; Psychology.

Bibliography

Barkow, Jerome, Leda Cosmides, and John Tooby, eds. The Adapted Mind: Evolutionary Psychology and the Generation of Culture. Oxford: Oxford University Press, 1992.

Buller, David J. Adapting Minds: Evolutionary Psychology and the Persistent Quest for Human Nature. Cambridge, MA: MIT Press, 2005.

Buss, David. Evolutionary Psychology: The New Science of the Mind. 2nd ed. Boston: Allyn and Bacon, 2003.

Buss, David. The Evolution of Desire: Strategies of Human Mating. New York: Basic Books, 1994.

Cosmides, Leda, and John Tooby. "Cognitive Adaptations for Social Exchange." In The Adapted Mind: Evolutionary Psychology and the Generation of Culture, edited by Jerome Barkow, Leda Cosmides, and John Tooby. Oxford: Oxford University Press, 1992.

Fodor, Jerry. The Mind Doesn't Work That Way: The Scope and Limits of Computational Psychology. Cambridge, MA: MIT Press, 2000.

Fodor, Jerry. The Modularity of Mind. Cambridge, MA: MIT Press, 1983.

Gould, Stephen Jay, and Richard C. Lewontin. "The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme." Proceedings of the Royal Society of London Series B 205 (1979): 581592.

Samuels, Richard. "Evolutionary Psychology and the Massive Modularity Hypothesis." British Journal for the Philosophy of Science 49 (1998): 575602.

Kelby Mason (2005)

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