262 III. DEvELOPMENT
Are Personality Traits  Consistent?
Determining personality traits’ consistency 
is fundamental to the field of personality 
psychology because it is definitional. The 
most frequently given definitions of person -
ality traits (e.g., the relatively enduring, au -
tomatic patterns of thoughts, feelings, and 
behaviors elicited in affording environments) 
all include consistency as a defining feature 
of personality. If personality, and especially 
personality traits, are not consistent, then 
the defining feature of the entire field is 
nullified, as well as one of the core features 
of how personality psychologists believe 
human nature is defined. However, “con -
sistency” has many meanings, and without 
a concrete point estimate definition of con -
sistency, one researcher’s “consistency” is a 
second researcher’s “variability,” and a third 
researcher’s “set like plaster.”
Despite these definitional ambiguities, the 
evidence for the “relatively enduring” na -
ture of personality traits appears to be suffi -
ciently high for researchers to conclude that 
the definitions of personality, and personal -
ity traits in particular, have merit. Since the 
earliest reviews of rank-order consistency, 
researchers have been reporting the same 
two findings: Personality traits demonstrate 
moderate to high rank-order consistency 
(i.e., correlations between .40 and .60) over 
reasonably long periods of time (i.e., 4–10 
years), and the longer one tracks rank-order 
consistency, the lower it gets (e.g., Fraley & 
Roberts, 2005). Moreover, personality traits 
increase in rank-order consistency through -
out the lifespan, peaking between the ages 
of 50 and 60, with a plateau or decrease 
after that decade. In addition, rank-order 
consistency does not vary markedly across 
the Big Five traits, assessment method (i.e., 
self- reports, observer ratings, and projec -
tive tests), or gender. The fact that five re -
views/meta-  analyses on the topic have been 
produced over the last few decades (Ardelt, 
2000; Bazana & Stelmack, 2004; Fergu -
son, 2010; Roberts & DelVecchio, 2000; 
Schuerger, Zarrella, & Hotz, 1989) testifies 
to the importance of the idea of personality 
consistency to the field.
A fair question at this juncture is whether, 
and to what extent, we can put more con -
crete parameters on the phrase “relatively 
enduring.” Some researchers use these levels of consistency as evidence that personality 
is unchanging (McCrae & Costa, 2008). 
While it appears that this finding only con -
tributes to the perspective that personality 
traits are unchanging, several things need 
to be kept in mind. First, the levels of con -
sistency, while substantial, are no more 
substantial than many other social science 
variables, such as the consistency of income 
or life satisfaction over time (Fujita & Die -
ner, 2005). Second, the levels of consistency 
never peak at unity—there is always less-
than-  perfect test–  retest stability, indicating 
that there is always room for change. Third, 
the estimates of consistency are bounded by 
the base of empirical data, which focuses 
most strongly on longitudinal studies track -
ing personality over moderate time spans 
such as 1–5 years. For example, the aver -
age time between tests in the Roberts and 
DelVecchio (2000) meta-  analysis was 7 
years, which was increased by the existence 
of a small number of studies that tracked in -
dividuals over several decades.
Then what is the level of continuity over 
much longer time windows? The answer is, 
surprisingly low. In fact, the most system -
atic estimates of the long-term stability of 
personality traits show that raw test–  retest 
stability appears to plateau around a cor -
relation of .20 (Fraley & Roberts, 2005), 
though this estimate was based on very 
little data that tracked stability beyond 20 
years. Since that review, several long-term 
studies have arrived at similar, if not lower, 
estimates of stability. In the 40-year follow 
up of the Hawaiian Longitudinal Study, 
most of the Big Five traits showed stabilities 
around .20, but the stability of neuroticism 
was conspicuously indistinguishable from 
zero. Similarly, in the longest study to date, 
individuals rated by their teachers at age 14 
on a set of traits described as dependability, 
showed zero stability when these scores were 
linked to observer ratings and self-  reports 
made when participants were 77 years old 
(Harris, Brett, Johnson, & Deary, 2016). 
The stability may have been zero in this lat -
ter study because the teacher ratings made 
in participants’ adolescence correlated more 
highly with cognitive ability than personal -
ity traits. In a more recent study stretching 
from ages 16 to 68 (Damian, Spengler, Sutu, 
& Roberts, 2019), self-  reported personality 
traits showed levels of consistency remark -