 14. Personality in Young Adulthood  331
distinctive effects on long-term changes in 
different personality traits.
Moderators of  Personality  Change
Various accounts of personality develop -
ment have stressed the role of moderators of 
personality change in the context of major 
life transitions. According to Caspi and 
Moffitt (1993), a life transition’s impact on 
personality change is likely moderated by 
the degree to which (1) previous behavior 
is discouraged and (2) clear information 
on how to behave is provided. Surprisingly 
little is known about these moderating vari -
ables, and much of current theorizing ap -
pears rather speculative. For example, it is 
possible that past behavior (e.g., partying 
a lot) would be discouraged after the birth 
of a child. However, the extent to which 
this behavior will be discouraged likely dif -
fers between individuals because of differ -
ent social norms or personal circumstances 
(e.g., if parents can afford a babysitter, they 
might occasionally go to parties). Moreover, 
to the extent that there are no clear and 
unambiguous normative scripts for appro -
priate responses, changes associated with 
a life transition might accentuate existing 
individual differences rather than triggering 
changes in personality traits (Caspi & Mof -
fitt, 1993).
According to social investment theory 
(Roberts, Wood, & Smith, 2005), another 
important moderator of personality change 
concerns the degree to which the individu -
al actively endorses the changes associated 
with a life transition. In particular, social 
investment theory proposes that personal -
ity change resulting from role transitions 
is most likely to occur if an individual psy -
chologically commits to the role in question. 
For example, whereas parenthood might 
generally be perceived as favorable for many 
individuals, some individuals might be less 
committed to the parent role and might per -
ceive the associated demands and challenges 
as an involuntary burden (e.g., in case of 
unwanted pregnancies). Researchers should 
therefore more actively investigate the qual -
ity of the life transition, and whether it is 
perceived negatively or positively, as a pos -
sible proxy for commitment (Lodi-Smith & 
Roberts, 2007).Implications for Future Research on Life 
Transitions and  Personality  Change
In this chapter, we have discussed the find -
ings of longitudinal research on life transi -
tions and personality trait change in young 
adulthood. These studies yielded mixed and 
sometimes conflicting results concerning 
the nature and direction of personality trait 
change in response to different life transi -
tions in young adulthood. The somewhat 
inconclusive nature of the current state of re -
search may be partly explained by the scope 
and methods of previous studies, many of 
which were not explicitly designed to exam -
ine personality change in response to major 
life transitions (Bleidorn et al., 2020). In view 
of both the recent accomplishments and the 
existing constraints of previous research, we 
conclude with several recommendations and 
open questions for future research on per -
sonality change and life transitions in young 
adulthood.
First, most previous studies were restricted 
by two-wave designs, which limit the analy -
ses to linear change models. In the case of 
many life transitions, however, nonlinear or 
discontinuous change models might be more 
suited to describe how change in personality 
traits unfolds before, during, and after a life 
transition (Luhmann, Orth, Specht, Kand -
ler, & Lucas, 2014; Schwaba & Bleidorn, 
2019). These models require longitudinal 
data with more than three measurement oc -
casions, a requirement that has been rarely 
met in previous research on life transitions 
and personality trait change.
Second, a key question concerns the 
timing of personality trait change dur -
ing major life transitions (Luhmann et al., 
2014). Change in personality traits may 
already have occurred before the initiation 
of a major life transition. For example, the 
critical affective, behavioral, and cogni -
tive changes associated with parenthood 
may occur long before the actual birth of a 
child. Forming the decision to have a baby 
or experiences during pregnancy may po -
tentially have a stronger influence on young 
adults’ personalities than the responsibili -
ties of parenthood (but see Van Scheppin -
gen et al., 2016). Other life transitions may 
have delayed effects on personality traits 
that unfold in a slow or incremental way. If 