346 III. DEvELOPMENT
of traits on health is a privilege, enjoyed by 
people who reside in social strata that have 
good access to health care and other health 
resources. If you have poor access to health 
resources, in a sense, your personality will 
not matter much. When infectious diseases 
are pervasive, with few doctors or hospitals 
around, it will not matter how conscientious 
you are. Polio will not discriminate among 
those with different personality trait levels. 
Thus, effects of personality on outcomes, 
and personality change itself, should vary 
across socioeconomic strata. Shanahan et 
al. hypothesizes that the effect of traits in 
health will diminish when resources that 
promote health are absent. They also theo -
rize that certain processes may hold in some 
parts of the lifespan but not others. Coping, 
planning, and risk avoidance process (re -
lated both to neuroticism and conscientious -
ness, and to personal goals) may be more 
salient in adolescence and young adulthood 
than in midlife or older adulthood. They 
call these “phase-  specific models,” because 
the mechanisms and processes are more rel -
evant during some phases of life than others. 
The Shanahan et al. proposal is inspired in 
its theoretical richness, but it remains more 
of a collection of fascinating concepts than 
a theory or even a framework. In addition, 
not many of the Roberts et al. (2008) or Sha -
nahan et al. (2014) ideas have been verified 
empirically. A number of multiyear research 
programs could be sustained by carrying out 
such verification.
In considering these new ideas, it is often 
valuable to look back. All of the aforemen -
tioned theories, frameworks, and concepts 
have roots in a well-known older model, 
lifespan developmental theory (Baltes, 
1987), which itself was grounded in an even 
older theory that emphasized individual dif -
ferences in change throughout life (Thomae, 
1968) but was not widely known outside 
Germany. Additionally, neo-  socioanalytic 
theory is also partly based on Helson’s so -
cial roles and social clock theory (Helson, 
Mitchell, & Moane, 1984), which itself 
is based on older theories. Many of these 
theories also make use of elements found in 
even older theories that have considered the 
topic of personality development in adult -
hood, notably, those of Allport and Murray. 
Allport’s concept of the cardinal trait, for example, can be integrated with newer con -
cepts, such as the idea of traits being evoca -
tive. The evocation of contexts may occur 
mainly for a given person’s cardinal traits. 
Extraversion in Oliver is cardinal and evokes 
all manner of responses from the environ -
ment. Yet conscientiousness is less cardinal 
and therefore less evocative. Future theorists 
of lifespan personality development would 
do well to blend some of this old wine with 
new, borrowing from some of the best ideas 
of the past.
Conclusion
Theory in the social and life sciences is 
mostly concerned with generalizing across 
people. Yet scholars of individual differenc -
es are mainly interested in variation across 
people. Theory pulls us toward Kluckhohn 
et al. (1953) statement, “We are like all oth -
ers,” but the central idea that animates per -
sonality science is individuality, exemplified 
by the complementary statement that “we 
are like no other person.” Any of the theo -
ries we mentioned earlier may apply to some 
people, but probably not to all people.
Therein lies the challenge for any theory 
of personality development. Individuality 
in trajectories will be abundant and defy 
efforts to generalize through a theory or 
even a framework. This is why stage theo -
ries, once so popular (e.g., those by Erikson 
and Kohlberg) fell out of favor by the 1990s. 
They tried to be too universal, arguing that 
all or most people pass through the various 
stages. Yet the recognition that individual 
differences are powerful and many people 
are not adequately described by rigid stage 
structures led to their demise.
The theories offered today need to be un -
derstood in the same light. If we know any -
thing as individual differences researchers, 
we know that there is wide variation among 
people and that a given theoretical principle 
may not hold for some individuals. Theories 
that incorporate this fact in a deep manner 
are likely to not only impart fundamental 
knowledge but also survive the dive into ir -
relevance that characterizes much of psycho -
logical theorizing. We offer two examples of 
successful theories. Lifespan developmental 
theory placed the notion of individual dif -