at this crucial period of the lifespan, where changes are substantial
enough to be studied. This ought to be a priority for future twin studies.
The third line of evidence is comparative. King and Figueredo
(1997) asked zookeepers from a large group of zoos to rate the person -
ality traits of chimpanzees, using a series of adjectives. Independent rat -
ings by different judges showed reasonably high levels of agreement,
suggesting that the ratings reflected something real in the animals’styles of behavior. When the ratings were factored, they found a largedominance factor (well known in studies of animal behavior), but theyalso found five other factors that resembled the factors in the humanFFM. Chimpanzees (at least in zoos) have a long lifespan, often livingto 50 years. When King, Landau, and Guggenheim (1998) correlatedthese factors with age, they found decreases in Neuroticism and in -
creases in Agreeableness (at least among females). It is possible that hu -
mans share with their nearest Primate relative a genetic program of per-
sonality development.
Why would such a program exist? Conceivably it has evolutionary
roots. Adolescents are high in Extraversion and Openness, whereasadults are high in Agreeableness and Conscientiousness. Perhaps at thestart of independent life it is advantageous to be adventurous (open andextraverted) to meet potential mates and to learn one’s way in theworld. Once settled down, Conscientiousness might well be helpful incarrying out the routine tasks of daily life and Agreeableness might bean asset in bonding with children. Interestingly , male chimpanzees arenot involved in raising the young and thus (in the present scenario)would have no evolutionary reason to become more agreeable as adults.And, in fact, they do not, according to King et al. (1998).
A few years ago the idea of comparative personality psychology
would have seemed ridiculous to many psychologists, but today it is apromising field of research (Gosling, 2001). With the possible exclusionof the Self-Concept, there is no reason why FFT could not be consid -
ered a theory of animal personality .
Changes in Individual Differences
Thus far we have been concerned with mean level changes, the norma -
tive developmental course of personality traits (e.g., the decline of Neu -
roticism with age). If everyone changed at exactly the same rate, retest
correlations would always be 1.0. But, in fact, we know that retest cor -A Five-Factor Theory of Personality 199