324 III. DEvELOPMENT
this hypothesis, the social vitality facet of ex -
traversion increases during emerging adult -
hood (between ages 18 and 22), followed by 
decreases during middle and late adulthood, 
whereas the social dominance facet of extra -
version shows gradual increases until age 40 
(Roberts et al., 2006).
In summary, personality traits under -
go systematic mean-level changes during 
young adulthood. The most robust trends 
are normative gains in emotional stability, 
agreeableness, and conscientiousness. These 
changes are consistent with the idea that 
individuals develop a more socially mature 
personality profile as they navigate the de -
velopmental tasks and life transitions that 
characterize young adulthood. In what fol -
lows, we provide a more formal definition 
of life transitions and present a general 
framework to explain how life transitions 
may lead to changes in different personality 
traits.
Life Transitions 
and Personality  Development
Life transitions  can be defined as “time- 
discrete transitions that mark the beginning 
or the end of a specific status” (Luhmann, 
Hofmann, Eid, & Lucas, 2012, p. 594), with 
status  referring to a certain position, rank, 
role, or condition. The transition from one 
status to another usually requires new be -
havioral, cognitive, or emotional responses. 
Theory and research suggests that those life 
transitions that involve clearly defined and 
unambiguous sets of behavioral, cognitive, 
or emotional demands are most likely to 
lead to enduring personality changes (Caspi 
& Moffitt, 1993; Kandler et al., 2012; Luh -
man, Fassbender, Alock, & Haehner, 2020; 
Neyer, Mund, Zimmermann, & Wrzus, 
2014; Roberts & Jackson, 2008; Specht et 
al., 2011).
For example, the transition to a commit -
ted romantic relationship usually requires 
certain behavioral changes, such as making 
plans and coordinating one’s daily life with 
one’s partner’s schedule. In these respects, 
people are required to act conscientiously 
in a serious partnership. To the extent that 
the transition to a committed relation -
ship indeed leads to changes in a person’s 
conscientiousness-  related thoughts, feelings, and behavior, and to the extent that these 
changes are stable and generalizable to other 
life domains, they should translate into 
broader and lasting trait changes.
The idea that life transitions affect person -
ality traits in a bottom-  up fashion through 
prolonged effects on an individual’s momen -
tary feelings, thoughts, and behavior is con -
sistent with the sociogenomic model of per -
sonality (Roberts & Jackson, 2008) and has 
important implications for the time course of 
personality trait change (Geukes, van Zalk, 
& Back, 2018). Specifically, to the extent 
that the behavioral, cognitive, and affective 
changes in response to life transitions unfold 
in a slow and incremental way, personality 
trait changes should unfold over relatively 
long periods. In contrast, if life transitions 
lead to abrupt and immediate changes in 
individuals’ behavioral, thoughts, and feel -
ings, we would expect sudden personality 
trait changes that unfold over shorter time 
periods.
In recent years, several longitudinal stud -
ies have examined whether personality traits 
change during major life transitions. We 
next review the literature on Big Five person -
ality trait change in response to four major 
life transitions in the domains of love and 
work that normatively occur during the pe -
riod of young adulthood: the first romantic 
relationship, parenthood, graduation from 
school/college, and the first job.
The First Romantic  Relationship
Several longitudinal studies have examined 
the impact of romantic relationships on Big 
Five personality trait change in young adult -
hood (for a review, see Bleidorn et al., 2018). 
These studies have typically compared the 
personality trajectories of young adults who 
entered a romantic relationship with the per -
sonality trajectories of individuals who were 
single and remained so throughout the study 
period. In an early study, Neyer and Asen -
dorpf (2001) used data from a representative 
sample of German young adults (ages 18–30 
years) who completed both personality and 
relationship measures at two measurement 
occasions across 4 years. They found that 
young adults who entered a romantic re -
lationship for the first time showed more 
pronounced decreases in neuroticism and 
increases in extraversion and conscientious -