be.”) Or perhaps she has been to an opera or two, found nothing of
interest, and concluded that opera was not for her. Being closed, shehas discovered that she is most comfortable being around down-to-earth, conventional people (McCrae, 1996), and they share and en -
courage her musical tastes. Her underlying closedness has influenced a
host of Characteristic Adaptations, which generally reinforce eachother.
The Origins of Traits
Where, then, do Basic Tendencies, specifically personality traits, origi -
nate? Here we come to the most controversial aspect of FFT. The Origin
postulate says that traits are endogenous Basic Tendencies, and in Fig -
ure 10, the only arrow leading into the Basic Tendencies component is
from Biological Bases. In contrast to virtually all other personality theo-ries, FFT does not admit of any influence of the environment on per-sonality traits (McCrae et al., 2000). This is a very radical position, andit is probably wrong in an absolute sense—that is, we are likely to findcircumstances in which the environment does have direct influences ontraits. Our intent, however, is to sketch a parsimonious model that ac-counts reasonably well for known facts, and we believe FFT does that.
The original basis for this position was, once again, the stability of
personality . We know that life changes for everyone over time, and itchanges dramatically for some people. If traits are shaped by the envi-ronment, we should expect considerable change in traits over time, asmost adult developmentalists did 20 years ago. But we find very littlechange. Therefore, traits must notbe shaped by the environment.
No one—including us—would accept that conclusion if the only
evidence were from longitudinal studies of personality stability . A singlesource of evidence is rarely enough to support so broad an interpreta -
tion. But there are several other lines of evidence that make Figure 10
more plausible.
Genetics
Consider first data on heritability . There is by now a very large body ofdata on the genetics of personality traits, from adoption studies (Loeh -
lin, 1992) to studies of twins raised in the same family (Jang et al.,
1996), to studies of twins separated at birth (Bouchard & McGue,A Five-Factor Theory of Personality 193