Chapter 15 Buss: Evolutionary Theory of Personality 443Environmental Sources
There are numerous ways in which the
environment contributes to adaptive indi-
vidual differences. Adaptive differences
increase reproductive success and one’s
chance of survival. One environmental
source of personality differences is what
Buss termed early experiential calibra-
tion, by which he meant that childhood
experiences make some behavioral strate-
gies more likely than others. An example
of such calibration is if people grow up
without a father present, they are more
likely to be sexually active at a young age
and have more sex partners during ado-
lescence and adulthood. People in this
situation cultivate a more promiscuous
sexual strategy because parental attention
is not reliable and adult relationships are
viewed as transient (Belsky, Steinberg, &
Draper, 1991).
Another example of early calibration
of adaptive strategies is attachment style, as
we first discussed in the Klein chapter (5).
Attachment between care-giver and infant is inherently adaptive—without such an
attachment the baby does not survive the first few weeks of life (Buss & Greiling,
1999). Adult attachment increases support, protection, and reassurance, and if attach-
ment is the model the child experiences, then he or she is likely to develop similar
relationships in adulthood. Similarly, avoidant attachment signals parental unwilling-
ness to invest in the child.
A second origin of environment induced individual differences is alternative
niche specialization, which means that different people find what makes them stand
out from others in order to gain attention from parents or potential mates. One
example of niche specialization is seen in birth order, as we saw in the Adler
chapter (3). Children of different birth orders gravitate toward different personali-
ties, interests, and activities because that is the only way to gain attention from
their parents. Frank Sulloway (1996) argued that first born find their “niche” by
identifying with parents and authority figures, whereas second and latter borns find
their “niche” by being focused on overthrowing those in power (i.e., older siblings).
Heritable/Genetic Sources
As we saw in the Eysenck and McCrae and Costa chapters, heritability is the extent
to which a trait is under genetic influence. Body type, facial morphology, and
degree of physical attractiveness act as heritable sources of individual differences
(Buss & Greiling, 1999). That is, muscular men or men with masculine, dominant
looks will garner more female attention, which will lead to more opportunities for
People who grow up without a father are
more likely to be sexually active early in
life. This is an example of what Buss calls
“early experiential calibration.”
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