Running head: Evolutionary psychology
Review of “Evolutionary psychology: The new science of the mind (2nd ed)” Dan Chiappe and Kevin MacDonald California State University, Long Beach
Correspondence to: Dr. Dan Chiappe Department of Psychology California State University, Long Beach 1250 Bellflower Blvd. Long Beach, CA 90840 USA Email:
[email protected] Phone: (562) 985-5024 Fax: (562) 985-8004 June 10, 2004
2 Evolutionary psychology This book is an introduction to the burgeoning field of evolutionary psychology (EP), written by one of its pre-eminent researchers, Professor David Buss. Targeted at an undergraduate audience, the book provides students with an account of key theories and research in various aspects of human nature. It is organized around classes of adaptive problems and their solution. These include various problems of survival, mating, parenting and kinship, cooperation and aggression, and problems in negotiating social hierarchies. In this edition, Buss has updated the text to include the most recent empirical research in this rapidly changing field. The result is a very readable and lucid statement of the EP position. Perhaps the greatest compliment one can pay is that it is one book that many of my students have said they are going to keep. As we will see below, however, a problem with this book is one that it shares with EP in general – it presents an incomplete view of human cognitive architecture. Chapter summaries The book is broken up into six parts. Part I provides the foundations of EP. Chapter 1 (The scientific movements leading to evolutionary psychology) provides the historical and conceptual background. This includes Darwin’s theories of natural and sexual selection, the modern synthesis of natural selection with gene theory, and the inclusive fitness revolution. Buss has also added a section on hominid evolution, removing an important omission from the first edition. Within psychology, ethology and sociobiology are discussed and contrasted with EP. The chapter also discusses behaviorism’s failure to explain the domain-specific propensities animals have to learn certain S-R connections. This is due to its equipotentiality assumption. A similar concern is raised with cognitive psychology, and the chapter ends by stating the need to integrate information-processing psychology with evolutionary considerations as a way of avoiding the combinatorial explosion plaguing cognitive theories. Chapter 2 (The new science of evolutionary psychology) outlines the EP position on cognitive architecture. It argues that human nature consists of highly specialized mechanisms, often referred to as modules. Each is designed to take in a narrow slice of information, and solve some specific problem of survival or reproduction that our ancestors regularly encountered. Arguments for massive modularity include that there are no reliable general procedures for solving the full range of adaptive problems, and
3 Evolutionary psychology that each adaptive problem possesses unique criteria for what constitutes a successful solution. The chapter also provides a useful sketch of different levels of evolutionary analysis (i.e., general evolutionary theory, mid-level evolutionary theories like parental investment theory, and specific hypothesis that follow from those mid-level theories). It also discusses the methods and types of evidence used to test hypotheses in EP. Part II examines problems of survival. Chapter 3 (Combating the hostile forces of nature) focuses mainly on food selection. Topics that are discussed include the antimicrobial hypothesis of spice consumption and pregnancy sickness as an adaptation for embryo protection. It also examines different theories regarding what led to our distinctive features as a species. The hunting hypothesis is presented as the most likely candidate, which accounts for tool use, large brains, complex language skills, and sex differences in spatial abilities resulting from a sexual division of labor. Buss also discusses prepared fears as an evolved solution for combating the threats posed by environmental dangers. The chapter ends with an examination of whether humans are programmed to die, focusing on senescence, the deterioration of all bodily mechanisms as organisms grow older, and invokes pleiotropy to explain this effect. It also examines whether suicide can be explained from an evolutionary perspective. Part III examines the challenges of sex and mating. Chapter 4 (Women’s long-term mating strategies) begins with a discussion of sexual vs. asexual reproduction. It also discusses parental investment theory as key for understanding the mating strategies of males and females. The chapter provides data from North American and international sources for the importance that women place on access to resources, social status, older age, ambition and industriousness, dependability, athletic prowess, good health, love and commitment, and the willingness to invest in children as criteria of a desirable longterm mate. It also discusses important contextual factors that affect women’s mate choices, including among other things, their own mate value. Chapter 5 (Men’s long term mating strategies) discusses benefits men accrue from long-term mating with women, as well as the characteristics that signify high mate value for men around the world. The focus is on features correlated with fertility and reproductive value, including youth and physical
4 Evolutionary psychology attractiveness. Averageness and symmetry are identified as two important aspects of facial beauty and a small waist to hip ratio as a key component of female body attractiveness. Buss also discusses adaptations for combating paternal uncertainty, examining the importance men place on chastity around the world. The chapter also discusses context effects affecting men’s mate choices, including the effects of social status, as well as the effects of viewing attractive models on satisfaction with one’s partner. Chapter 6 (Short-term sexual strategies) begins by discussing the costs and benefits of short term mating to men, and adaptive problems they must solve in pursuing this strategy. It uses parental investment theory to explain men’s stronger propensity for short term mating. It also discusses evidence for a long history of selection pressures for short term mating (e.g., relative testicle size, variations in sperm insemination, gender differences in sexual fantasies, etc.). Buss also discusses hypotheses about why women engage in short term mating, focusing on benefits such as added resources, superior genes and the honing of mating skills. The chapter also includes a discussion of contextual factors that affect a woman’s propensity for short term mating, including stepfather presence, self-perceived mate value, and ratio of males to females. Part IV examines the challenges of parenting and kinship. Chapter 7 (Problems of parenting) examines why women provide more parental care than men. Reasons include paternal uncertainty, that men can abandon offspring sooner, and that men suffer more mating opportunity costs from investing in offspring. Buss also examines the factors that mechanisms of parental care should be sensitive to in determining how much to invest in offspring. These include genetic relatedness, the ability of the offspring to convert parental care into reproductive success, and whether there are alternative uses of resources. These factors are used to explain child abuse, infanticide, degree of financial investment in offspring, and the female tendency to boost confidence in paternity in their men by noting their resemblances to the newborns. The chapter also discusses parent-offspring conflict stemming from a genetic conflict of interest. Chapter 8 (Problems of kinship) outlines inclusive fitness theory and the evolvability constraints on kin altruism specified by Hamilton’s rule. It also discusses universal features of kinship systems.
5 Evolutionary psychology These include that they make distinctions on the basis of gender and generation, as well as on dimensions of “closeness,” factors influencing degree of cooperation and solidarity. Evidence supporting inclusive fitness theory is also discussed, including research on alarm calls in ground squirrels, and in humans, helping behavior, as well as patterns of the inheritance of wealth across generations. The chapter also uses inclusive fitness theory to explain why the father’s father is the least likely grandparent to invest in grandchildren and why the mother’s mother is the most likely to do so. The chapter ends by discussing the evolution of the family unit, and by exploring some of the sources of familial conflict. Part V examines problems of group living. Chapter 9 (Cooperative alliances) begins by outlining the theory of reciprocal altruism. It also discusses the tit-for-tat strategy for ensuring cooperation in the prisoner’s dilemma situation. Buss also discusses examples of cooperation in animals including vampire bats, vervet monkeys, and chimpanzees. Social contract theory is also discussed, which specifies the mechanisms required for adaptively engaging in social exchange. This includes remembering individuals, and whether or not they cheated in previous exchange situations. Buss discusses evidence for such cheater-detection mechanisms using Wason’s selection task where people have to detect violations of conditional rules. People are much more successful at detecting cheaters of social contract rules (e.g., “if you drink alcohol, you must be 21 years old”) than violations of abstract rules (e.g., “if there is a vowel on one side of a card, there is an even number on the other side”). Buss ends with a discussion of the psychology of friendship, including the basis of opposite sex friendships. Chapter 10 (Aggression and warfare) examines adaptive problems for which aggression can provide a solution. These include: co-opting other’s resources, inflicting costs on intra-sexual rivals, and negotiating status hierarchies. Buss also explains why males are more aggressive than females. This is due to differences in the variance of reproduction between the sexes, causing males to adopt riskier strategies. The chapter also discusses adaptations required for the evolution of warfare including, among other things, a “veil of ignorance” about who will live or die. Barring this, individuals would be unlikely to engage in coalitional warfare. The chapter ends by discussing whether we have evolved homicide mechanisms that motivate people to kill conspecifics under certain circumstances.
6 Evolutionary psychology Chapter 11 (Conflict between the sexes) discusses strategic interference theory, which holds that conflict arises when one person prevents the successful enactment of a strategy another person is using to attain a goal. Much of the conflict between the sexes has to do with men seeking sexual access sooner, and women delaying the granting of sexual access. Buss also discusses whether men have adaptations leading them to rape under certain situations, and if females have evolved adaptations for minimizing the chances that they will be victims. The chapter also discusses cross-cultural evidence for sex differences in jealousy responses, with men being more upset by sexual infidelity and women by emotional infidelity. Tactics of mate retention are also discussed, including sex differences in the use of such tactics (e.g., men using more resource displays, while women using appearance enhancement). Chapter 12 (Status, prestige, and social dominance) examines the fact that many animals form dominance hierarchies, where individuals at the top receive more status and access to resources. Animal examples that are discussed include crayfish and chimpanzees. In the case of humans, Buss discusses sex differences, explaining why males score higher on measures of status striving, as well as differences in the way males and females express their dominance. The chapter also discusses Cummins’ dominance theory, which holds that people have reasoning mechanisms specialized for reasoning about social norms involving hierarchies. This includes permissions, obligations, prohibitions, etc. Another theory of dominance that is discussed is the social attention-holding theory. On this view, people compete to receive positive attention from, and to be valued by, other people. The chapter also discusses some indicators of dominance, including testosterone levels, serotonin levels, walking speed, and size. Part VI, consisting of Chapter 13 (Toward a unified evolutionary psychology), discusses how EP can provide a conceptual framework that can integrate the otherwise disparate areas of psychology. It also shows how EP has important implications for each of these fields. In cognitive psychology, EP yields insights about cognitive architecture (e.g., its alleged domain specificity), as well as informing content areas including reasoning and language. EP theories can also shed light on the phenomena of social psychology. This includes: why people form mateships, friendships, coalitions, and ties with kin. In developmental psychology, issues like attachment patterns in infants can be seen as adaptations to
7 Evolutionary psychology particular familial contexts. Within personality psychology, concepts such as frequency-dependent adaptations can help explain some heritable individual differences. In clinical psychology, insights from EP can, among other things, be used to define mechanism dysfunction and offer insights into problems that are erroneously thought to be dysfunctions. Cultural psychology also benefits from EP’s conceptual apparatus. It can help, for example, understand why human males are more prone to create cultural displays (e.g., books, music, art) than human females. Critique Buss’s book is a clear statement of the EP position. Indeed, it accepts EP arguments regarding the domain-specificity of cognitive architecture whole-heartedly, and therein lies the problem. EP offers an incomplete picture of the mind and fails to make sense of important areas of human cognition, particularly our ability to innovate – our ability to solve novel problems and to invent novel solutions to longstanding problems (Chiappe and MacDonald, in press). EP construes the environment of evolutionary adaptedness (EEA) as a set of recurring problems and the cues that can be exploited in their solution. Psychological mechanisms evolve to solve specific adaptive problems that have endured over many generations (e.g., identifying fertile women), and they do so by exploiting particular cues correlated with biologically relevant information (e.g., the waist to hip ratio). The result is a collection of dedicated intelligences. The problem is that the EEA associated with hominids was hardly a period of stability (Potts, 1998; Richerson and Boyd, 2000). The geological record suggests environmental fluctuations became increasingly extreme, especially during the Pleistocene. These climate oscillations led to substantial remodeling of the EEA. As Potts (1998) says, “shifts between dense, moist forest and cold dry steppe occurred repeatedly during the past 1 million years over large regions” (p. 83). Humans and other mammals were forced to adapt to inconsistent selection pressures that, rather than being irrelevant, led to the evolution of mechanisms capable of responding to novel problems as opposed to being specialized for particular environmental conditions. As Potts says, “Pleistocene hominids became less inclined to track
8 Evolutionary psychology particular habitats as change occurred and more capable of adjusting to novel conditions and the increasing range of oscillation” (1998, p. 93). The difficulty presented by novel problems is that, by definition, an organism cannot rely on an innately specified procedure provided by a dedicated intelligence. Instead, it has to improvise a solution. Central to this ability is general intelligence (g). General intelligence, particularly fluid intelligence, is the ability to solve problems characterized by minimal background knowledge. As Gottfredson and Dreary (2004) say, “High intelligence is a useful tool in any life domain, but especially when tasks are novel, untutored, or complex, and situations are ambiguous, changing, or unpredictable” (p. 2). Despite the volumes of evidence showing the importance of g in predicting success in various aspects of life (including health and longevity, Gottfredson and Dreary, 2004) the treatment it receives in Buss’ text is virtually nil. The book also fails to discuss research into mechanisms underlying general intelligence that have been studied for years by cognitive psychologists. One such mechanism is working memory, which has been identified as an important component of the ability to solve novel problems (e.g., Bechelder and Denny, 1977; Engle, Tuholski, Laughlin and Conway, 1999; Kyllonen and Christal, 1990). Working memory is a mechanism consisting of executive mechanisms, along with some short-term memory stores. The executive functions are involved in controlling attention. They have the functions of activating representations relevant for a current task, while inhibiting potentially distracting representations and other pre-potent responses. The executive functions, rather than the storage functions, have been found to predict individual differences in fluid intelligence (Engle, et al., 1999). The executive functions play an important role in problem solving. They are crucial for planning and goal management. Goal management involves constructing, maintaining and executing a mental plan of action during the solution of a novel problem. In goal management we set up a hierarchy of subgoals that need to be fulfilled to achieve a higher-level goal. People with low working memory capacities have trouble keeping relevant goals active, and hence fail to solve problems appropriately (e.g., Kane, Bleckley, Conway and Engle, 2001).
9 Evolutionary psychology Also absent from Buss’s text is a discussion of analogical reasoning. Analogy, of course, is a process that is central to human creativity and our ability to innovate (Chiappe, 2000; Holyoak and Thagard, 1995). Research in cognition has found that presenting people with source analogues can facilitate problem solving (e.g., Gick and Holyoak, 1980). It is a truly domain-general process, which finds applications in diverse areas including scientific inquiry, in technology, in legal decision-making, in political thought, and is also ubiquitous in natural language (Holyoak and Thagard, 1995). Analogical reasoning is closely associated with measures of general intelligence; it has a high loading on g. Sternberg (1977) reports correlations ranging from .68 to .84 between tests of general intelligence and tests of analogical reasoning. This is likely because analogical reasoning involves a conscious, controlled, comparison process that draws heavily on the resources of working memory (Kyllonen and Christal, 1990; Waltz, Lau, Grewal, and Holyoak, 2000). It requires both a storage component, and an attention-demanding processing component – two hallmarks of working memory tasks. Analogies require that the elements of the analogies and their properties be maintained in active state, while we search for abstract commonalities between the domains. At the same time, we need to inhibit potentially distracting features of the two domains, features that may interfere with our ability to see relevant similarities underlying the surface differences (Gentner and Holyoak, 1997). In short, Buss’s book deals at length with relatively automatic and unconscious mechanisms that have evolved to solve recurrent challenges of our evolutionary past. It fails to address how it is that humans manage to solve novel problems and invent new solutions to longstanding problems. A distinction offered by Stanovich (1999) is useful in this regard, a distinction between System 1 and System 2 mechanisms. System 1 consists of mechanisms that are “automatic, largely unconscious, and relatively undemanding of computational capacity” (p. 144). System 2 consists of mechanisms that involve controlled, attention-demanding processing. An important difference between these two is that System 1 contextualizes problems, while System 2 is used to decontextualize them. Contextualization means that the mechanisms involved automatically bring to bear as much prior knowledge as is easily accessible. In contrast, System 2 consists of “processes that often operate to strip excess content and
10 Evolutionary psychology context from representations generated by System 1 (Stanovich, 1999, p. 193). Thus, one of the jobs of System 2 is to sometimes override the automatic and obligatory computations provided by System 1. An example would be the situation where a person has to evaluate the validity of an argument, where the premises and the conclusion of an argument are known to be false. While System 1 would alert us to the falsehood of the propositions, System 2 would have to override this, and judge whether the argument is nonetheless valid on the basis of the logical connection between premises and conclusion. Decontextualization is essential in situations where one is engaging in planning. In planning we imagine what would happen if a certain course of action was taken. This requires that we decouple representations from the context of what System 1 tells us is the case. The ability to decontextualize representations depends on the executive functions, which inhibit representations that can interfere with current processing goals. Decontextualization is also essential to analogy, where relations embedded within a domain are abstracted from their particular content areas and applied to novel domains. Furthermore, there is much evidence supporting the connection between decontextualization and general intelligence. People who do well on one task that involves decontextualization (e.g., abstract versions of Wason’s selection task) also tend to do well on other decontextualized tasks (e.g., judging the strength of arguments for which one doesn’t agree with the conclusions), and they also tend to be individuals scoring high on g (Jensen, 1998; Stanovich, 1999). Measures of g, however, do not predict variability in performing System 1 operations. For instance, performance on cheater-detection versions of the selection task is not predicted by measures of general intelligence (Stanovich, 1999). In short, Buss’s textbook, like the field of EP in general, does ample justice to System 1 processes — the various modules that we have for dealing with recurrent problems in the evolutionary past. However, it fails to do justice to System 2 processes. There is nothing in the EP paradigm, for instance, that explains why some people successfully manage to solve abstract versions of the Wason selection task, or other abstract logical problems, or how it is that people manage to invent novel solutions to longstanding problems by employing such tools as analogical reasoning. One hopes that future editions of Buss’s text will devote some chapters to such quintessential human abilities.
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12 Evolutionary psychology Sternberg, R. (1977). Intelligence, information processing, and analogical reasoning: A componential analysis of human abilities. Hillsdale: Erlbaum. Waltz, J., Lau, A., Grewal, S. & Holyoak, K. (2000). The role of working memory in analogical mapping. Memory & Cognition, 28, 1205–1212.
