Traits and trade-offs are insufficient for evolutionary personality psychology

Comments on the article by D. Nettle, who has clearly shown that evolutionary psychologists need to focus more attention on individual differences, not just species-typical universals. Such differences are not mere "noise," and evolutionary theory will gain by understanding how they are produced and maintained. However, by focusing on personality traits and the five-factor personality model, Nettle left unaddressed many of the most important aspects of human personality. An evolutionary psychology of personality must ultimately explain not just trait differences but also differences in personal goals, values, motives, identities, and life narratives--essential elements of human individuality and functionality. K. M. Sheldon et al suggest four reasons why traits and the five-factor personality model do not provide an optimal approach for explaining the evolution of personality: (a) As constructs, traits provide little purchase for explaining the causes of behavior; (b) trait concepts do not acknowledge or explain people's variations around their own baselines, variations that are likely crucial for adaptation; (c) traits do not explain or even describe true human uniqueness, i.e. the ways in which a person is different from everybody else; and (d) traits do not explain personality from the inside, by considering what people are trying to do in their lives. In raising these issues Sheldon et al are suggesting that the important question for evolutionary personality study is not why people fall at different points on a continuum regarding traits x, y, and z, but rather why each person is inevitably unique while still sharing the same evolved psychology.