Evaluating the Trait Approach

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Chapter 11 Personality
children’s personalities tend to resemble the personalities of their biological parents and
siblings more closely than they do those of the families in which they are raised (Plomin
et al., 1998).
Further research will determine more clearly what aspects of the environment are
most important in shaping personality (Turkheimer & Waldron, 2000). So far, the evidence suggests that personality is not influenced very strongly by elements of the shared
environment—such as socioeconomic status—that equally affect all children in the
same family. However, nonshared environmental influences, at home and elsewhere,
appear to be very important in personality development (Harris, 2000; Loehlin,
Neiderhiser, & Reiss, 2003). We need to know more about the exact impact on personality development of nonshared environmental factors that may be different for
twins and nontwin siblings.
■ What conclusions are most reasonable?
Even those researchers, such as Robert Plomin, who support genetic theories of personality caution that we should not replace “simple-minded environmentalism” with
the equally incorrect view that personality is almost completely biologically determined
(Plomin & Crabbe, 2000). It is pointless to talk about heredity versus environment as
causes of personality, because nature and nurture always intertwine to exert joint and
simultaneous influences (Dodge, 2004; Johnson, McGue, & Krueger, 2005).
With this caution in mind, we would be well advised to draw only tentative conclusions about the origins of personality differences. The evidence available so far suggests that genetic influences do appear to contribute significantly to the differences
among people in many personality traits (Plomin & Crabbe, 2000). As noted earlier,
however, there is no evidence of a specific gene for any specific personality trait. The
genetic contribution to personality most likely comes as genes influence people’s nervous systems and general predispositions toward certain temperaments (Arbelle et al.,
2003; Ebstein, 2006; Grigorenko, 2002). Temperamental factors (e.g., emotionality and
sociability) then interact with environmental factors, such as family experiences, to produce specific features of personality (Caspi et al., 2005). For example, children who
inherit a tendency toward emotionality might play less with other children and withdraw from social interactions and thus tend to fail to learn important social skills
(Eisenberg, Fabes, & Murphy, 1995). These experiences and tendencies, in turn, might
foster the self-consciousness and shyness seen in introverted personalities.
Notice, though, that genetic predispositions toward particular personality characteristics may or may not appear in behavior, depending on whether the environment supports or stifles them. Changes in genetically predisposed traits are not only possible but
may actually be quite common as children grow (Cacioppo et al., 2000). So even though
there is a strong genetic basis for shyness, many children learn to overcome this tendency
and become quite outgoing (Rowe, 1997). In summary, rather than inheriting specific
traits, people appear to inherit the behavioral and emotional raw materials out of which
their personalities are shaped by the world.
Evaluating the Trait Approach
The trait approach, and especially the big-five model, tends to dominate contemporary
research in personality. Yet there are several problems and weaknesses associated with
this approach.
For one thing, trait theories seem better at describing people than at understanding
them. It is easy to say, for example, that Marilyn is nasty because she has a strong hostility trait; but other factors, such as the way people treat her, could also be responsible. In other words, trait theories say a lot about how people behave, but they don’t
always explain why (Mischel, 2004a, 2004b). Nor do trait theories say much about how
traits are related to the thoughts and feelings that precede, accompany, and follow