CHAPTER 8 The Evolutionary Psychology of the Emotions and Their Relationship to Internal Regulatory Variables JOHN TOOBY and LEDA COSMIDES Evolutionary psychology is an attempt to unify The discovery of a correct information- the psychological, social, and behavioral sci- processing description of a psychological ences theoretically and empirically within a mechanism is the fundamental clarifying scien- single, mutually consistent, seamless scientific tific step, because each mechanism came into framework. The core of this enterprise is the in- existence and was organized by natural selec- tegration of principles and findings drawn tion in order to carry out its particular set of from evolutionary biology, cognitive science, information-processing functions. It is not a anthropology, economics, and neuroscience metaphor but a reality that the brain is a with psychology in order to produce high- computer—a physical system that came into resolution maps of human nature. By “human existence to carry out computations. The com- nature,” evolutionary psychologists mean the putations were needed to solve the adaptive evolved, reliably developing, species-typical problem of regulating behavior successfully. computational architecture of the human Hence the brain (and its subsystems) evolved to mind, together with the physical structures and carry out specific varieties of computation in processes (in the brain, in development, and in order to regulate behavior so that it was bio- genetics) that give rise to this information- logically successful—that is, to assemble the in- processing architecture. For evolutionary psy- dividual somatically and neurally, to prevent chologists, all forms of knowledge about brains prereproductive death, to increase the proba- and behavior are relevant, but the pivotal step bility of achieving conditions (social and physi- is using these facts to form accurate models of cal) that would have led to successful reproduc- the information-processing structure of psy- tion in the ancestral world, to reproduce chological mechanisms. successfully, and to assist genetic relatives (in- 114 8. The Evolutionary Psychology of the Emotions 115 cluding children) to achieve and maintain con- not limited to one area of human life, such as ditions for their own successful reproduction. sex, violence, or resource acquisition. Instead, In short, the functional subcomponents (pro- it is a dimension cross-cutting all areas of grams) that constitute our psychological archi- human life, as weighted by the strange, tecture were designed by natural selection to nonintuitive metric of their cross-generational solve adaptive problems faced by our hunter– statistical effects on direct and kin reproduc- gatherer ancestors by regulating behavior in tion. ways that increased genetic propagation— By “computation,” evolutionary psycholo- what biologists call “fitness.” Against the oth- gists simply mean the organized causation of erwise disordering forces of entropy that per- patterned information input–output relations. vade all of physical reality, natural selection is Natural selection poses adaptive problems of the only process that introduces functional or- behavior regulation, and the mechanisms of the ganization into the designs of organisms brain evolved to engineer solutions in the form (Tooby, Cosmides, & Barrett, 2003). So, to the of these regulatory input–output relations. Of extent that there is functional organization in course, these computational relations must be the human psychological architecture, it was embodied physically in neural tissue, and must created by, reflects, and is explained by the be designed to develop reliably. Adaptations operation of natural selection among our an- are not just the products of the genes, but are cestors. This is why evolutionary psychology is the products of the coordinated interaction of a not a specific subfield of psychology, such as stable genetic inheritance and the evolution- the study of vision, reasoning, or social behav- arily long-enduring features of the environ- ior. It is a way of approaching the science of ment. psychology that produces (or is intended to A model of an evolved neurocomputational produce) stable functional descriptions of the mechanism or program would answer ques- elements of the mind. (Detailed arguments for tions such as these: What information does the these positions can be found in Tooby & program take as input? How is this infor- Cosmides, 1990a, 1990b, 1992a, 2005, and in mation encoded, formatted, and represented Cosmides & Tooby, 1987, 1992, 1997.) as data structures? What operations are per- Researchers less familiar with evolutionary formed on these data structures to transform psychology often equate adaptive problems ex- them into new representations or regulatory el- clusively with short-run threats to physical sur- ements? And how do these procedures and vival. However, survival per se is not central to data structures interact to generate and regu- evolution: All individual organisms die sooner late behavior? In short, how does each pro- or later. In contrast, genes—which can be gram work in cause-and-effect terms? thought of as particles of design—are poten- tially immortal, and design features spread by promoting the reproduction of the genes that AN EVOLUTIONARY- participate in building them. Survival is signifi- PSYCHOLOGICAL APPROACH cant only insofar as it promotes the reproduc- TO THE EMOTIONS tion of design features into subsequent genera- tions. Survival is no more significant than Although an evolutionary-psychological ap- anything else that promotes reproduction, and proach can be applied to any topic in psychol- is often advantageously risked or sacrificed in ogy, it is especially illuminating when applied the process of promoting reproduction in self, to the emotions. To the extent that there is children, or other relatives. Nearly every kind functional order to be found in the mechanisms of event or condition has the potential to have responsible for the emotions, it was forged over some impact on the prospect of reproduction evolutionary time by natural selection acting for individuals, their children, and their rela- on our ancestors. The analysis of adaptive tives. Consequently, selection on neural designs problems that arose ancestrally has led evolu- for functional behavior reaches out to encom- tionary psychologists to apply the concepts and pass, in a network of cause and effect linkages, methods of the evolutionary sciences to scores virtually all of human life, from the subtleties of topics that are relevant to the study of emo- of facial expression to attributions of responsi- tion. These include anger, cooperation, sexual bility to the intrinsic rewards of play. The realm attraction, jealousy, aggression, parental love, of adaptive information-processing problems is friendship, romantic love, the aesthetics of 116 I. INTERDISCIPLINARY FOUNDATIONS landscape preferences, coalitional aggression, exploration new empirical and theoretical pos- incest avoidance, disgust, predator avoidance, sibilities obscured by other frameworks. kinship, and family relations (for reviews, see Barkow, Cosmides, & Tooby, 1992; Buss, 2005; Crawford & Krebs, 1998; Daly & Wil- AN EVOLUTIONARY- son, 1988; Pinker, 1997). PSYCHOLOGICAL THEORY Indeed, a rich theory of the emotions natu- OF THE EMOTIONS rally emerges out of the core principles of evo- lutionary psychology (Tooby, 1985; Tooby & Both deductions from theoretical evolutionary Cosmides, 1990a; Cosmides & Tooby, 2000; psychology and a large supporting body of em- see also Nesse, 1991). In this chapter, we (1) pirical findings in psychology, biology, and briefly state what we think emotions are and neuroscience support the view that the human what adaptive problem they were designed to mental architecture is crowded with evolved, solve; (2) explain the evolutionary and compu- functionally specialized programs. Each is tai- tational principles that led us to this view; (3) lored to solve a different adaptive problem that identify how the emotions relate to motiva- arose during human evolutionary history (or tional and other underlying regulatory vari- before), such as face recognition, foraging, ables the human brain is designed to generate mate choice, heart rate regulation, sleep man- and access; and (4) using this background, ex- agement, or predator vigilance, and each is ac- plicate in a more detailed way the design of tivated by a different set of cues from the envi- emotion programs and the states they create. ronment. It may strike some as odd to speak about But the existence of all these diverse programs love, jealousy, or disgust in computational itself creates an adaptive problem: Programs terms. “Computation” has an affectless, fla- that are individually designed to solve specific vorless connotation. But if the brain evolved as adaptive problems could, if simultaneously acti- a system of information-processing relations, vated, deliver outputs that conflict with one an- then emotions are, in an evolutionary sense, other, interfering with or nullifying each other’s best understood as information-processing functional products. For example, sleep and relations—that is, programs—with naturally flight from a predator require mutually inconsis- selected functions. Initially, the commitment to tent actions, computations, and physiological exploring the underlying computational archi- states. It is difficult to sleep when your heart and tecture of the emotions may seem