Better than Rational: Evolutionary Psychology and the Invisible Hand @ Leda Cosmides; John Tooby The American Economic Review, Vol. 84, No. 2, Papers and Proceedings of the Hundred and Sixth Annual Meeting of the American Economic Association (May, 1994), 327-332. Stable URL: http://links.jstor.org/sici?sici=0002-8282%28199405%2984%3A2%3C327%3ABTREPA%3E2.O.CO%3B2-9 The American Economic Review is currently published by American Economic Association. Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/about/terms.html. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.j stor.org/journals/aea.html. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is an independent not-for-profit organization dedicated to creating and preserving a digital archive of scholarly journals. For more information regarding JSTOR, please contact [email protected]. http://www.jstor.org/ Fri Sep 10 17:38:04 2004 Better than Rational: Evolutionary Psychology and the Invisible Hand Several years ago, we attended an inter- Gigerenzer, 1991). And for the many behav- disciplinary seminar on what were pur- ioral domains where standards of rationality ported to be "biases" in negotiation be- are unclear or undefined, economics is havior. The economists, psychologists, and presently mute. biologists present were mulling over the data From a broader scientific perspective, this when, suddenly, a prominent economist lit formulation is decidedly odd. Rational be- up. "Ah, I see,'" he said, "behavior is either havior is not, in any sense, the state of rational or it's psychological." nature. Not behaving at all is the state of This formulation stuck in our minds, be- nature in a universe that includes lifeless cause it seemed to succinctly give voice to a planets, prebiotic soup, mountains, trees, tacit assumption held by many economists and tables. All departures from this state of -one that we think works to the detriment inaction require explanation. Moreover, the of economics, by isolating it from the rele- behavioral repertoires of various animals vant parts of biology, psychology, and the differ profoundly from one another, and rest of the natural sciences. This assump- this must be explained as well: bats cannot tion is that rational behavior is the state of speak, and we cannot navigate through nature, requiring no explanation. Explana- echolocation. Humans and other animals tions that invoke the cognitive processes reason, decide, and behave by virtue of that actually generate human choices are computational devices embodied in neural required only when behavior deviates from tissue. Therefore, a complete causal expla- this state of nature. In this view, economics nation of any behavior-rational or other- is grounded in assumptions of rational be- wise-necessarily invokes theories about the havior, is theoretically constructed out of architecture of these computational devices. what logically follows from assuming ratio- The rationality of a behavior is irrelevant to nal behavior, and gains specificity by plug- its cause or explanation. ging in a variety of variables that are kept Every economic model entails theories exogenous to economics, such as prefer- about these computational devices, but they ences. Merchants of the ad hoc and exoge- are usually left implicit, buried in the as- nous, psychologists are called in only to sumptions of the model. At the moment, provide second-order corrections to eco- most economists rely on the implicit (and nomic theory, usually by furnishing a cata- somewhat vague) theory that these compu- log of oddities and quirks in human reason- tational devices somehow embody "rational" ing (e.g., "biases" and "fallacies"-many of decision rules. But developing a more accu- which are turning out to be experimental rate, useful, and well-defined substitute for artifacts or misinterpretations; see G. this black box is now a realistic goal. Results from the newly emerging field of evolution- ary psychology suggest that (i) explicit, well-specified models of the human mind *Department of Psychology, University of Califor- can significantly enhance the scope and nia, Santa Barbara, CA 93106, and Department of specificity of economic theory, and (ii) ex- Anthropology, University of California, Santa Barbara, plicit theories of the structure of the human CA 93106, respectively. For enlightening discussions, mind can be made endogenous to economic we warmly thank Gerd Gigerenzer, Robert Nozick, models in a way that preserves and expands and Paul Romer. For financial support, we are grateful to the McDonell Foundation and NSF Grant No. their elegance, parsimony, and explanatory BNS9157-449 to Tooby. power. 32 7 328 AEA PAPERS AND PROCEEDINGS MAY 1994 At present, economics hovers, scientifi- of relationships that link inputs to outputs, cally unsupported and isolated in mid-air, can deduce the structure of a computer theoretically levitating on the assumption of program. Hence cognitive scientists can ask: rationality. But this is unnecessary and lim- do our brains embody procedures that carry iting. There are tight causal and analytic out the rules of logical inference? or calcu- connections between economics, psychol- late Bayesian probabilities? or cause us to ogy, and evolutionary biology (Tooby and avoid incest? or allow us to echolocate? Cosmides, 1992a): Of course, the information-processing structure of the mind is fantastically com- 1. Natural selection-an invisible-hand plex, so conducting experiments blindly, process-is the only component of the without knowing what to look for, has not evolutionary process that produces com- been an efficient research strategy. This is plex functional machinery in organisms, where the integration of evolutionary biol- such as the vertebrate eye (Richard ogy and cognitive science has proved so Dawkins, 1986). useful. The applicability of evolutionary bi- 2. Natural selection built the decision-mak- ology is based on a simple but powerful ing machinery in human minds. idea. Form follows function: the properties 3. This set of cognitive devices generates all of an evolved mechanism reflect the struc- economic behavior. ture of the task it evolved to solve. 4. Therefore, theories of economic behav- This approach has teeth because there is ior necessarily include theories about the only one class of problems that evolution structure of the cognitive mechanisms produces mechanisms for solving: adaptive that generate that behavior. Moreover, problems. These are problems that recurred the design features of these devices de- across many generations during a species' fine and constitute the human universal evolutionary history, and whose solution principles that guide economic decision- statistically promoted reproduction in an- making. cestral environments. By identifying and modeling the adaptive problems humans In other words, natural selection's invisible faced during their evolution, researchers can hand created the structure of the human make educated guesses about the designs of mind, and the interaction of these minds is the complex computational devices the hu- what generates the invisible hand of eco- man brain embodies, and about many of the nomics (e.g., Tooby and Cosmides, 1992a): specific design features they required to be one invisible hand created the other. able to solve these problems. Armed with these models, researchers can then design I. Evolutionary Psychology experiments that can detect and map the features of these complex devices-features The brain is a complex computational that no one would otherwise have thought device, a system that takes sensory informa- to test for. tion as input, transforms it in various ways, stores it, analyzes it, integrates it, applies 11. A New View of the Mind decision rules to it, and then translates the output of those rules into the muscular con- The application of these methods is lead- tractions that we call "behavior." For the ing to a fundamentally new view of the most part, humans have no more conscious architecture of the human mind. Previously, access to the structure of these programs the mind was thought to resemble a gen- and the decision rules they embody than to eral-purpose computer: initially free of any the processes through which the kidneys content that had not originated in the senses select what to excrete. Nevertheless, the and the social world (the tabula rasa as- structure of these information-processing sumption), and equipped only with a small programs can be mapped in much the same number of content-independent rules of in- way that a programmer, by studying the web ference (e.g., rules drawn from logic, mathe- VOL. 84 NO. 2 INVISIBLE-H AND THEORIES 329 matics, and probability theory, or associa- ral problems is the primary reason why tive rules). problem-solving specializations were fa- Converging lines of evidence from an ar- vored by natural selection over general-pur- ray of disciplines are replacing this view pose problem-solvers. Despite widespread with a model in which the human