 6. Temperament  161
later in life (Roberts et al., 2006). Similarly, 
DvC scores also decline with age, decreasing 
during both young adulthood and middle 
age (Roberts et al., 2006). In addition, Rob -
erts et al.’s meta-  analysis indicated that the 
A- and C-  related aspects of the trait show 
differential patterns over time. Specifically, 
C increased substantially between ages 22 
and 40, and showed much more change 
overall; in contrast, A exhibited less overall 
change and displayed the largest increases 
later in life (Roberts et al., 2006, Tables 6 
and 7).
Finally, the findings regarding E/PE have 
been much more inconsistent (Roberts et al., 
2006; Vaidya et al., 2002). However, Rob -
erts, Robins, Trzesniewski and Caspi (2003) 
found that the data were more consistent at 
the specific trait level: Measures of domi -
nance tended to increase from adolescence 
through early middle age, whereas levels 
of sociability increased during adolescence, 
then declined starting in young adulthood. 
In a related vein, Roberts et al. (2006) found 
that social dominance scores increased con -
sistently throughout young adulthood and 
stabilized thereafter. In contrast, social vital -
ity levels tended to be highly stable through -
out most of the lifespan before showing a 
modest decline late in life.
Taken together, the available data indicate 
that mean-level changes are both meaning -
ful and highly systematic across the lifespan. 
Indeed, Caspi et al. (2005) concluded that 
they reflect a maturity principle,  arguing 
that these mean-level shifts “point to in -
creasing psychological maturity over devel -
opment, from adolescence to middle age” 
(p. 468). We must note, however, that virtu -
ally all of the relevant longitudinal evidence 
comes from participant self-  ratings. More -
over, in an analysis of a relatively large new -
lywed sample, Watson and Humrichouse 
(2006) found that spouse-  rated personal -
ity displayed a very different pattern over a 
2-year interval, showing significant decreas -
es in C, A, O, and E/PE over time. Interest -
ingly, spouse ratings also showed evidence of 
a “honeymoon halo effect,” such that they 
tended to be more positive than self-  ratings 
at time 1, but 2 years later tended to be more 
negative. It should be noted, however, that 
Oltmanns, Jackson, and Oltmanns (2020) 
reported stronger convergence between self- versus informant-  rated change in a sample 
of older adults. Taken together, these results 
highlight the value of collecting  multimethod 
data in adult personality development stud -
ies.
Rank‑Order  Stability
Data on the extent to which individuals 
maintain their relative position on trait con -
tinua over time are quite consistent and yield 
several clear conclusions. First, stability cor -
relations for personality traits are moderate 
to strong in magnitude, even when assessed 
in childhood and adolescence (Caspi et al., 
2005; Roberts & DelVecchio, 2000). Thus, 
the stability of personality is not simply a 
characteristic of adulthood, but emerges 
early in life.
Second, stability correlations decline in 
magnitude as the time interval increases 
(Caspi et al., 2005; Roberts & DelVecchio, 
2000; Watson, 2004). This consistent pat -
tern has helped to establish the existence of 
true change in personality, given that change 
is more and more likely to occur with in -
creasing retest intervals (Watson, 2004). It 
must be emphasized, however, that stability 
correlations never approach .00 and remain 
at least moderate in magnitude, even across 
several decades (Fraley & Roberts, 2004).
Third, stability correlations for personal -
ity increase systematically with age (Caspi et 
al., 2005; Kandler, 2012; Roberts & DelVec -
chio, 2000). Older models of trait develop -
ment assumed that most personality change 
occurred prior to the age of 30, after which 
stability correlations should be uniformly 
high (for a discussion, see Roberts & DelVec -
chio, 2000). However, the meta-  analytic 
findings of Roberts and DelVecchio revealed 
that stability coefficients for personality con -
tinue to increase well into middle age.
Fourth, the available evidence indicates 
that rank-order stability coefficients essen -
tially are invariant across methods (Caspi 
et al., 2005; Roberts & DelVecchio, 2000; 
Watson & Humrichouse, 2006). Most no -
tably, in their meta-  analytic review of the 
literature, Roberts and DelVecchio (2000, 
Table 4) obtained virtually identical popula -
tion estimates of overall trait stability across 
self- report ( r = .52) and observer-  rated ( r = 
.48) data.