336 
Clyde Kluckhohn and Henry Murray’s 
(Kluckhohn, Murray, & Schneider, 1953, 
p. 358; we take note of the outdated sex -
ist language of the 1950s) famous maxim 
about personality (we are all “like all men, 
like some other men, like no other man”) es -
sentially argues for a general level of simi -
larity, a middle level, and a specific or idio -
syncratic level where there is little similarity. 
The course of personality development in 
adulthood can be described in parallel 
terms. Personality trajectories, whether they 
track traits or other aspects of personality 
(personal action constructs, life narratives, 
etc.; McAdams, 2015) are manifested at 
these three tiers of similarity. First, there 
is a general, overall population-  level trajec -
tory that describes the movement of a per -
sonality construct across all people. Second, 
there are trajectories specific to a given sub -
group. These “middle trajectories” can cor -
respond to a country, a demographic group, 
or a sample or study. Often, they diverge 
from the overall (population) trajectory, and 
in multistudy analyses, it is frequently ob -
served that there is a great deal of variation 
in these sample-  level trajectories (e.g., Gra -ham et al., 2020). Third and last, there are 
personality trajectories at the level of the in -
dividual. Within any study or sample, these 
are captured by estimates of individual vari -
ation in level (intercept) and rate of change 
(slope) and, theoretically, illustrate the lifes -
pan principle of individual differences in 
intraindividual change (Baltes, 1987; Muel -
ler, Wagner, & Gerstorf, 2017). The Kluck -
hohn et al. (1953) idea of individual differ -
ences being organized around a (1) general 
or population level, (2) a subgroup level, 
and (3) an individual level can inform how 
we think about personality development in 
adulthood.
Hence, we use this concept of nested tra -
jectories as an overarching organizational 
theme in this chapter. In the following pages, 
we first describe our own three-level frame -
work of personality trajectories (population, 
subgroup, individual), describing method -
ological issues that touch on the ability to 
estimate high-  quality trajectories, replica -
bility of trajectories, and the notion of het -
erogeneity in trajectories over subgroups. 
We then summarize the empirical evidence 
regarding personality change in adulthood, CHAPTER 15
Personality Development in  Adulthood 
and Later Life
Daniel K. Mroczek  
Eileen  K. Graham  
Nicholas  A. Turiano  
Mazeed Omotilewa Aro -Lambo