Theories of Personality 9th Edition

Chapter 15 Buss: Evolutionary Theory of Personality 445

few generations (cf. O’Steen et al., 2002). Note too, these traits are heritable
and have a genetic basis, which is one criterion for an adaptation.
Similarly, Nettle (2006) recently expanded on evolutionary theories of
personality and argued that Tooby and Cosmides’s (1990) argument that personality
could not be an adaptation failed to appreciate how environmental change and
variability would ultimately select for individual differences in behavior within a
given species. Nettle (2006) reviewed numerous studies from the nonhuman animal
literature that report how sudden changes in the environment (just a few genera-
tions), increased the proportion of animals that had traits adaptive to that environ-
ment. When the environment switched back to the original conditions, animals on
the other end of that dimension became more common again. For example, some
female chickadees are bold and exploratory, whereas others are inhibited. In food-
poor years, the more exploratory birds are most likely to survive (Dingemanse,
Both, Drent, & Tinbergen, 2004). In food-rich years, however, the bolder and more
exploratory female birds are less likely to survive, possibly because they are more
likely to become involved in dangerous encounters with predators. In short,
evolution favors individual differences because one can never predict what the
future holds and which qualities will best match changes in the environment.
Furthermore, Nettle (2006) hypothesized there have been fitness costs and
benefits of each of the Big Five dimensions of personality during ancestral periods
of evolution (see Table 15.2). For example, benefits of being extraverted include
being more successful at mating, making social allies, and exploring one’s environ-
ment, whereas evolutionary costs of extraversion include taking more physical risks
and having potentially a less stable family (i.e., more affairs). A benefit of being
open to experience is heightened creativity, and its costs are having more unusual
beliefs and possibly even developing psychosis. High levels of conscientiousness
have the benefit of causing one to pay closer attention to the details of physical

TABLE 15.2

Costs and Benefits of Big Five Dimensions of Personality (Nettle, 2006)

Domain Benefits Costs

Extraversion Mating success; social allies; Physical risks; family stability

exploration of environment

Neuroticism Vigilance to dangers; striving and Stress and depression, with

competitiveness interpersonal and health

consequences

Openness Creativity, with effect on Unusual beliefs; psychosis

attractiveness

Conscientiousness Attention to long-term fitness Missing of immediate fitness

benefits; life-expectancy and gains; obsessionality; rigidity

desirable social qualities

Agreeableness Attention to mental states of Subject to social cheating;

others; harmonious interpersonal failure to maximize selfish

relationships; valued coalitional advantage

partner

From Nettle (2006), copyright American Psychological Association; reprinted with permission.