Understanding Psychology (10th Ed)

FIGURE 4 
The inherited roots of personality. The percentages indicate the degree to which 
11 personality characteristics refl ect the infl uence of heredity. 
(Source: Tellegen et al., 1988.)
temperament 
The innate disposition 
that emerges early in life.
researchers using biological and evolutionary approaches argue that personality is 
determined at least in part by our genes in much the same way that our height is 
largely a result of genetic contributions from our ancestors. The evolutionary per-
spective assumes that personality traits that led to our ancestors’ survival and repro-
ductive success are more likely to be preserved and passed on to subsequent 
generations (Buss, 2001, 2009). 
Twin studies illustrate the importance of genetic factors in personality. For 
instance, personality psychologists Auke Tellegen and colleagues at the University 
of Minnesota examined the personality traits of pairs of twins who were genetically 
identical but were raised apart from each other (Tellegen et al., 1988; Bouchard, et 
al., 2004). In the study, each twin was given a battery of personality tests, including 
one that measured 11 key personality characteristics. 
The results of the personality tests indicated that in major respects the twins were 
quite similar in personality, despite having separated at an early age. Moreover, cer-
tain traits were more heavily infl uenced by heredity than others. For example, social 
potency (the degree to which a person assumes mastery and leadership roles in social 
situations) and traditionalism (the tendency to follow authority) had particularly 
strong genetic components, whereas achievement and social closeness had relatively 
weak genetic components (see Figure 4). 
Furthermore, it is increasingly clear that the roots of adult personality emerge 
in the earliest periods of life. Infants are born with a specifi c temperament, an innate 
disposition. Temperament encompasses several dimensions, including general 
activity level and mood. For instance, some individuals are quite active, while others 
are relatively calm. Similarly, some are relatively easygoing, while others are irritable, 
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