Psychologists agree that environmental factors interact with genetic
factors to form personality. Some psychologists have proposed theories that
emphasize these genetic influences on personality.
Hans Eysenck’s Theory
Psychologist Hans Eysenck believes that genetics are the
primary determinate of personality, although he thinks conditioning also plays a
role. According to Eysenck, personality traits are hierarchical, with a few
basic traits giving rise to a large array of more superficial traits.
Genetically determined differences in physiological functioning make some people
more vulnerable to behavioral conditioning. Eysenck suggests that introverted
people have higher levels of physiological arousal, which allows them to be
conditioned by environmental stimuli more easily. Because of this, such people
develop more inhibitions, which make them more shy and uneasy in social
situations.
Empirical evidence for genetic contributions to personality comes mainly
from two kinds of studies: studies of children’s temperaments and heritability
studies.
Studies of Temperament
Temperament refers to innate personality features or
dispositions. Babies show particular temperaments soon after birth.
Temperaments that researchers have studied include reactivity, which refers
to a baby’s excitability or responsiveness, and soothability, which refers
to the ease or difficulty of calming an upset baby.
Researchers have studied children from infancy to adolescence and found
that temperaments remain fairly stable over time. However, temperaments can also
be modified over time by environmental factors.
Heritability Studies
Heritability studies also provide evidence for genetic contributions to
personality. Heritability is a mathematical estimate that indicates
how much of a trait’s variation in a population can be attributed to genes. For
more information about heritability, see page 35.
