344 III. DEvELOPMENT
This is another reason why studies with an 
outcome representing a clear endpoint (onset 
of substance use: Hampson et al., 2010; 
mortality: Mroczek & Spiro, 2007) can 
help sort out causal direction, as we men -
tioned earlier. Studies of personality change 
may benefit in particular from use of a clear 
endogeneous variable, as it strengthens the 
argument that the personality change that 
preceded it played some role in the outcome 
actually being triggered.
Recent Theory in Adult 
Personality  Development
We end where most other authors begin. 
However, it is useful to assess what the data 
say first, before considering theory. This is 
especially true at present, when many large-
scale longitudinal datasets have finally ac -
crued multiple waves of measurement, per -
mitting better data-based inquiries than 
were possible in years past. Yet the last de -
cade has been a period of fertile theorizing 
as well.
Perhaps the most prominent conceptual 
framework to emerge in last 10–15 years 
is the neo-  socioanalytic theory (Roberts & 
Wood, 2006). Social roles form the center -
piece of this theory, along with the identity 
expectations that come with adopting par -
ticular roles. Roles also have reputational 
characteristics that impact on personal -
ity development, thus involving interactions 
with observers and other people external to 
the actor. Social role changes drive personal -
ity change, but such change is not limitless 
and is bounded by genetic and physiological 
factors. It is a comprehensive theory, taking 
into account nearly all of the known influ -
ences on lifespan personality development. 
It also contains certain ideas that have been 
shown to be mostly consistent with avail -
able data, most notably the corresponsive 
principle (e.g., Jackson, 2011) and the social 
investment principle (e.g., Bleidorn et al., 
2013). We described corresponsiveness ear -
lier. Social investment  refers to age-  graded 
changes, or investments, in social roles (par -
ent, worker, partner) that lead to personality 
changes. There are studies that show no sup -
port for social investment, especially with 
respect to parenting roles (Mund, Zimmer -man, & Neyer, 2018), but in general the so -
cial investment principle seems to align with 
data. Among lifespan personality develop -
ment theories, the neo-  socioanalytic theory 
probably enjoys the largest base of confirm -
ing evidence.
However, many of the trait changes pre -
dicted by neo-  socioanalytic theory (in -
creasing conscientiousness, extraversion, 
openness, and agreeableness in young and 
midadulthood; declining neuroticism in 
young and midadulthood) are not consistent 
once older adulthood arrives. After midlife, 
there is evidence for decreases in all or nearly 
all of the Big Five traits (Berg & Johansson, 
2014; Kandler et al., 2015; Lucas & Donnel -
lan, 2011; Mõttus, Johnson, & Deary, 2012; 
Roberts & Mroczek, 2008).
One of the more theoretically compelling 
explanations for these reversals in later life 
is Baltes’s (1997) concept of selective opti -
mization with compensation (SOC), which 
holds that development includes both gains 
and losses across the entire lifespan, whereas 
older adulthood is usually defined mostly by 
losses. In order to optimize development in 
older adulthood, individuals compensate 
for these losses and also engage in selection 
behaviors by restricting goals and activities 
in domains where functionality has become 
impaired (Baltes, 1997). As noted by Kan -
dler et al. (2015) and Mueller et al. (2016), 
SOC theory may be applied to personality 
development to explain trait trends that ap -
pear to decelerate or even reverse in older 
adulthood. For example, developing and 
maintaining work and career goals, along 
with relevant skills, may become less of a 
priority or drop out entirely as a priority in 
later life, thereby exerting downward pres -
sure on trait conscientiousness. In another 
example, the need to be on guard regarding 
health and financial risks in older adulthood 
may bring SOC process to bear on trait neu -
roticism. SOC, in combination with neo- 
socioanalytic theory (especially its maturity 
principle), may provide the most comprehen -
sive explanation for how personality chang -
es and develops throughout the full lifespan.
A number of other recent theories are cen -
tered on dynamic regulatory mechanisms 
that govern personality development. Denis -
sen, van Aken, Penke, and Wood (2013) 
have proposed a theory of self-  regulated 