232 II. BIOLOGICAL  FOuNDATIONS
Zealand, in which personality and work 
experiences were measured at ages 18 and 
26. In general, lower levels of negative emo -
tionality, reflecting lower stress reaction, 
aggression, and alienation, and higher lev -
els of positive emotionality and constraint, 
reflecting especially greater social closeness, 
social potency, and self-  control, were associ -
ated with greater occupational attainment, 
work satisfaction, work involvement, finan -
cial security, and work autonomy and stimu -
lation (Roberts et al., 2003). In the second 
study, Roberts and Robins (2004) measured 
the fit between person and environment as 
the correlation between consensus ratings 
of qualities of a university environment and 
individual perceptions of the ideal univer -
sity environment over a period of 4 years in 
305 university students from the Berkeley 
Longitudinal Study; they found that greater 
academic aptitude and emotional stability, 
male sex, and lower agreeableness were as -
sociated with better fit. In combination with 
the knowledge that all these traits show 
substantial genetic influence, these studies 
suggest inferences about the transactions 
between genetic and environmental influ -
ences that allow stable personality traits to 
contribute to the emergence of individual -
ized environmental niches.
But such transactions between genetic 
and environmental influences contribute 
to personality change as well as stability. 
Caspi and colleagues’ (2005) coresponsive 
principle summarizes the process. Accord -
ing to this principle, life experiences tend to 
reinforce the personality characteristics that 
originally draw people to those experiences. 
The easygoing, cheerful child who expresses 
affection naturally is well received by oth -
ers and quickly establishes friendships that 
build further social skills and a solid basis 
of positive emotional experience, developing 
and deepening the trait we think of as extra -
version. In contrast, the stress-  reactive, so -
cially awkward child who is easily angered 
is frequently rebuffed by others and quickly 
becomes resentful and alienated, developing 
and deepening the trait we think of as ag -
gression. In the language of life-  course dy -
namics and the psychopathology literature, 
the coresponsive principle links the process 
of social selection, in which people seek 
experiences that are correlated with their 
personality traits, with the process of social causation, in which experiences affect per -
sonality traits. In the language of behavior 
genetics, the coresponsive principle links ac -
tive rGE, in which the correlation between 
environmental and genetic influences results 
from niche building, with passive and evoca -
tive rGE, in which the correlation between 
environmental and genetic influences arises 
from growing up with family members simi -
lar to oneself and from the responses of oth -
ers to genetically influenced behavioral dis -
plays.
The two studies described earlier ad -
dressed the coresponsive principle as well as 
niche building. In the Dunedin sample (Rob -
erts et al., 2003), young adults at age 26 who 
attained higher-  status jobs and jobs that 
involved acquisition of resource power be -
came more socially dominant, harder work -
ing, happier, and more self-  confident. Those 
who found more satisfying work tended to 
become less anxious and less prone to stress. 
Work involvement was associated with in -
creases in willingness to work hard and sup -
port for conventional norms. Those who 
attained greater financial security tended 
to become less prone to stress and better 
adjusted socially. Confirmation of the core -
sponsive principle was evidenced by the fact 
that these same personality characteristics at 
age 18 had predicted the age-26 occupation -
al outcomes. In the Berkeley sample (Rob -
erts & Robins, 2004), fit improved a little 
over the course of the study, primarily be -
cause students’ views of the ideal university 
environment changed to more closely match 
the actual university environment. In addi -
tion, students who fit better with the univer -
sity environment underwent less personality 
change, and fit between person and environ -
ment was associated with increases in emo -
tional stability and decreases in agreeable -
ness. In both these studies, influences were 
not dramatic but they were consistent, and 
the samples consisted of young adults. Many 
people are still just embarking on their oc -
cupational careers at age 26, so actual career 
outcomes are far from clear. College atten -
dance itself is a period of transition for most 
people. Thus, we could anticipate greater co -
responsive effects and clearer indications of 
niche building over longer time frames.
In summary, life experiences and the situ -
ations in which people find themselves do 
not occur randomly, unilaterally bringing 