 14. Personality in Young Adulthood  327
self- control during the transition to parent -
hood. Specifically, using prospective four-
wave data from 539 Dutch young adults, 
they compared mean-level changes in self- 
control as reported by first-time parents ( n 
= 246) to participants without children ( n 
= 293). Although parents reported higher 
levels of self-  control before birth, especially 
mothers underwent significant decreases in 
self- control. Moreover, pregnancy-  related 
stress was associated with lower self-  control 
levels during pregnancy in both first-time 
mothers and first-time fathers.
Like marriage and other normative life 
transitions, the birth of a child is not a ran -
dom event. In all modern Western societ -
ies, the birth of a child is usually a planned 
event and reflects an individual choice. This 
implies that putative socialization effects of 
childbirth are likely confounded with selec -
tion effects (i.e., the choice to have a child). 
In fact, parents and individuals without chil -
dren differ systematically in a large number 
of socioeconomic, social, and psychologi -
cal characteristics, including their person -
ality traits (Hutteman, Bleidorn, Penke, & 
Denissen, 2013; Jokela et al., 2009; Jokela, 
Alvergne, Pollet, & Lummaa, 2011). To sta -
tistically account for these selection effects, 
Van Scheppingen et al. (2016) used propen -
sity score matching techniques and two-
wave longitudinal data from a representative 
Australian panel study (HILDA) to compare 
personality trait changes in first-time par -
ents and nonparents across a 4-year period. 
Before using propensity score matching, par -
ents differed significantly from nonparents 
with regard to change in extraversion and 
conscientiousness. Consistent with previous 
studies (Specht et al., 2011), the unmatched 
results indicated that parents but not non -
parents decreased in these two traits. How -
ever, after using propensity score matching, 
the differences between parents’ and non -
parents’ trait changes were no longer signifi -
cant, suggesting that some of the observed 
differences may be due to selection rather 
than socialization processes.
In summary, research on personality 
change during the transition to parenthood 
has yielded mixed results. Some researchers 
found positive changes, as indicated by in -
creases in new fathers’ extraversion (Jokela 
et al., 2009); others found negative change, 
as indicated by decreases in traits related to conscientiousness (Specht et al., 2011; Van 
Scheppingen et al., 2019); and still others 
found no differences between new parents 
and nonparents (Van Scheppingen et al., 
2016). Thus, although the transition to par -
enthood is one of the most salient life transi -
tions in young adulthood, few studies indi -
cate strong support for robust associations 
between this transition and maturation in 
personality traits.
Graduation from  School and  College
Graduation from some form of schooling 
is an almost universal life event during the 
transition from late adolescence to young 
adulthood. The experience of attending and 
graduating from school and/or college has 
been theorized to be particularly relevant for 
changes in young adults’ conscientiousness 
and openness to experience (e.g., Bleidorn 
& Schwaba, 2017; Lüdtke, Roberts, Traut -
wein, & Nagy, 2011).
To examine the impact of high school 
attendance and graduation on personality 
change, Bleidorn (2012) examined a sample 
of German high school students in a longi -
tudinal design with three assessment waves. 
Specifically, this study compared the per -
sonality trait changes in 360 high school 
seniors over three assessment waves before 
and after graduation with those observed 
in a comparison group of 550 high school 
juniors. Despite a very short observation 
period of only 1 year, this study revealed 
significant mean-level changes in different 
Big Five traits. Senior students experienced 
significant increases in conscientiousness 
(d = 0.34), agreeableness ( d = 0.24), and 
openness ( d = 0.25), and to a lesser degree 
also decreases in neuroticism ( d = –0.07). 
Notably, these trait changes were most pro -
nounced during the first two assessments 
before and immediately after graduation. 
The subsample of juniors who completed 
all measurements while still enrolled in high 
school showed significantly less pronounced 
increases in conscientiousness ( d = 0.20) 
and openness ( d = 0.22) than seniors and no 
changes in agreeableness and neuroticism.
A further result of this study was that, 
compared to their classmates, those senior 
students who invested more time and effort 
in studying showed more pronounced in -
creases in conscientiousness and openness 