Cross-cultural research is not the only source of support for FFT.
Think of the studies of nonhuman animal personality (Gosling, 2001).Because animals have a biology somewhat different from that of hu -
mans, the details of FFT would not be expected to be the same, but the
general model should be applicable. Any pet owner will confirm thatdogs and cats have enduring personality traits, that they form relation -
ships (loving and hostile) with others in their world, that they have
habits and preferences, that they act and experience across their wholelives. Animal psychology fits easily into the framework of FFT, but it ishard to imagine a psychoanalytic, or social role, or humanistic theory ofanimal personality . The fact that the common sense of pet owners isnow being scientifically attested (King & Figueredo, 1997; Gosling &John, 1999) can be considered another testimonial to FFT.
It seems likely that progress in molecular genetics and in brain im -
aging will soon lead to the identification of some of the Biological Bases
postulated in FFT, and more direct tests of the theory will then be possi-ble. For example, there are differences in the mean levels of traits acrosscultures (McCrae, 2000a). FFT asserts that these are biologically based,and genes are the major candidates to explain these bases. Once wehave identified the form of a gene (or more likely genes) that underlieExtraversion, we can make a prediction: These forms (or alleles) will befound with higher frequency in cultures that score higher on measuresof Extraversion. Such tests are particularly appealing, because genes canbe assayed with scientific objectivity and great precision. We need notworry about translations or response sets or the cultural interpretationof items. Of course, personality traits are not genes, they are psychologi -
cal constructs. But genes may give us a more objective indicator of traits
than we have ever had.
***
In Chapter 2 we gave a definition of traits as dimensions of individual dif -
ferences in tendencies to show consistent patterns of thoughts, feelings, and
actions . That definition applies to populations rather than to people (be -
cause people don’t have dimensions; instead, they are characterized by
their standing on various dimensions), and it pertains to the phenotype,the observable manifestation of traits. We are now in a position to givean alternative definition of traits that applies directly to people and thatpertains to the genotype, the underlying causal basis: T raits are endoge -204 PERSONALITY IN ADULTHOOD