 34. Personality and Subjective Well‑Being 733
time, cross-twin correlation was .40 in the 
identical twins. Because this cross-twin, 
cross-time correlation is 80% as large as the 
stability coefficient, Lykken and Tellegen es -
timated that 80% of the stable component of 
well-being is heritable. They suggested that 
this extremely high heritability means that 
“trying to be happier [may be] as futile as 
trying to be taller” (p. 189).
There are three reasons why this conclu -
sion may be too extreme (also see Roysamb 
et al., 2014 for a discussion). First, as Rut -
ter (1997) noted, estimates of heritability 
“provide no unambiguous implications for 
theory, policy, or practice” (p. 391). In other 
words, even if Lykken and Tellegen’s (1996) 
estimate of heritability is correct, this does 
not necessarily mean that happiness cannot 
be changed. Until the mechanisms by which 
these genetic effects work are discovered, 
questions about the possibility for change 
remain even when the heritability is known 
to be strong.
Second, the high heritability only refers 
to the part of happiness that is stable over 
time, and this makes up only about half of 
the variance at any given wave in Lykken 
and Tellegen’s (1996) study. Furthermore, 
these stability estimates appear to be at the 
upper bound for what is typically found in 
longitudinal studies of SWB. As we review 
in the section on stability, most studies find 
10-year stabilities that are somewhat lower 
than that found by Lykken and Tellegen. 
Thus, even if the stable component was 
100% heritable and completely unchange -
able, there would still be considerable room 
for change.
Finally, Lykken and Tellegen’s (1996) con -
clusion is based on a single study with a rela -
tively small sample of twins. Although a more 
recent study has replicated these findings in a 
much larger sample (Nes, Roysamb, Tambs, 
Harris, & Reichborn-  Kjennerud, 2006), 
a second study has not. Johnson, McGue, 
and Krueger (2005) presented cross-twin, 
cross-time correlations that suggest 38% 
of the stable variance in well-being is heri -
table (though they did not set out to address 
this question and did not explicitly analyze 
their data in this way). The major difference 
between these two samples was age of the 
participants. Johnson and colleagues’ study 
included older adults, whereas the study by Nes and colleagues (2006) and the original 
Lykken and Tellegen (1996) study included 
a sample of participants in their 20s. Thus, 
with only three studies available, the replica -
bility of this more controversial effect (along 
with the role that age plays in this effect) 
cannot be evaluated.
Stability of  SWB
For decades, psychologists have recognized 
that there is considerable stability in people’s 
affective and cognitive evaluations of their 
lives. This stability is reflected both in the 
consistency of individuals’ affective reac -
tions to distinct situations and in the main -
tenance of their relative level of global hap -
piness over time. For instance, in his early 
studies on the consistency of personality, 
Epstein (1979) showed that affect during any 
single day correlates relatively weakly with 
affect on any other day. However, once af -
fect is aggregated over multiple days, strong 
correlations emerge. Similarly, momentary 
affect was assessed across multiple situa -
tions using the experience sampling method 
(Diener & Larsen, 1984). Like Epstein, they 
found that moment-  to- moment correlations 
were quite weak. However, once affect rat -
ings were aggregated within similar types 
of situations, average levels of affect were 
highly consistent over time and across situ -
ations. For instance, average positive affect 
at work correlated .70 with average positive 
affect experienced during recreation. Simi -
larly, average negative affect at work corre -
lated .74 with average negative affect during 
recreation. Thus, there are stable individual 
differences in the levels of positive and nega -
tive affect that emerge even across diverse 
situations.
Of course, cross-  situational consistency 
does not guarantee long-term stability; 
therefore, to determine whether happiness 
can change, it is necessary to conduct lon -
gitudinal studies over very long periods of 
time. Results of such studies show that the 
various SWB components exhibit moderate 
long-term stability. For instance, Schimmack 
and Oishi (2005) conducted a meta-  analysis 
of existing studies that had examined the 
stability of life satisfaction measures. Not 
surprisingly, they found that stability de -
creased with increasing intervals. However, 