154 II. BIOLOGICAL  FOuNDATIONS
Lifestyle: Daily Rhythms and Sleep
Biologically based diurnal and seasonal 
rhythms are observed in many important 
behaviors of plants and animals; human be -
havior is no exception. For example, there 
is strong and consistent diurnal variation in 
mood: PA—but not NA—shows a roughly 
sinusoidal curve that tracks with other bodi -
ly cycles, such as body temperature (Clark 
et al., 1989; Thayer, 1989; Watson, 2000; 
Watson et al., 1999). Given that mood is a 
core feature of temperament, it is plausible 
that individual differences in daily behavior 
might reflect underlying variations in tem -
perament. Research examining variation in 
diurnal mood cycles due to temperament, 
however, has been quite inconsistent, sug -
gesting that there is no simple relation be -
tween temperament and daily mood rhythms 
(e.g., Clark et al., 1989). However, to inves -
tigate whether temperament might influ -
ence other aspects of daily behavior, we had 
students in Sample 2 record the number of 
hours they slept each day, whereas students 
in Sample 4 kept a daily log of their rising 
and retiring times, from which we computed 
total hours of sleep. The Sample 4 students 
also completed a revised version (Smith, 
Reily, & Midkiff, 1989) of the Horne and 
Ostberg (1977) Morningness–  Eveningness 
Questionnaire (MEQ).
There was no relation between hours of 
sleep and either N/NE or E/PE in either 
study; this “nonfinding” is consistent with 
the prior literature, which has found few 
simple or straightforward relations between 
diurnal rhythms and general affective tem -
perament (E. Gray & Watson, 2002). In 
Sample 2, amount of sleep correlated mod -
estly with DvC ( r = .27, p < .01), with those 
high in disinhibition sleeping longer. In 
Sample 4, however, when actual rising and 
retiring times were recorded, so that we cal -
culated students’ sleep time rather than hav -
ing them estimate it themselves, this relation 
disappeared.
It is noteworthy, however, that although 
there was no clear relation with total sleep 
amount, there were significant associations 
between temperament and when  students 
slept. First, disinhibited individuals both 
retired and arose later ( r’s = .33 and .36, 
respectively; p < .001). Moreover, this ef -fect related significantly more to the DvC 
Carefree Orientation (low C) subscale ( r’s 
= .39 and .43, respectively) than to Antiso -
cial Behavior (low A; r ’s = .19, p ’s < .05 and 
.14, nonsignificant). Similarly, disinhibited 
individuals displayed a more characteristic 
“night owl” orientation on the MEQ than 
did those low in disinhibition ( r = –.27), 
with a much stronger relation observed for 
Carefree Orientation ( r = –.34) than Anti -
social Behavior ( r = –.08). Similarly, E. Gray 
and Watson (2002, Table 5) found that DvC 
was associated significantly with later rising 
and retiring times in a 7-day sleep log, with 
a particularly strong effect for the Carefree 
Orientation subscale.
Conversely, individuals high in E/PE were 
more likely to be “morning larks” (MEQ r = 
.34, p < .01) and to record both earlier ris -
ing (r = –.17, p < .07) and retiring times ( r = 
–.21, p < .03, respectively). Further analysis 
using the two GTS Positive Temperament 
subscales yielded interesting results. The 12-
item Energy subscale reflects the more purely 
physical aspects of the dimension that likely 
are tied more directly to biological param -
eters (e.g., “Most days I have a lot of ‘pep’ or 
vigor” and “I can work hard, and for a long 
time, without feeling tired”). The Positive 
Affectivity subscale items, by contrast, are 
more laden with cognitive content (e.g., “I 
lead a very interesting life” and “I can make 
a game out of some things that others con -
sider work”). The subscales are substantially 
related ( r = .57), so strongly differential cor -
relates are relatively rare; nevertheless, both 
earlier rising time ( r’s = –.19 vs. –.06) and 
MEQ scores ( r’s = .33 vs. .23) related sig -
nificantly more to the Energy than to the 
Positive Affectivity subscale. (Curiously, 
however, retiring time was equally related to 
Energy and Positive Affectivity.) Although 
these relations are not strong, nor the dif -
ferences large, they clearly suggest that sleep 
behavior is tied more closely to the physical 
and biological (vs. social and cognitive) as -
pects of positive temperament.
Lifestyle: Substance Use, Criminality, Sexuality, 
and Spirituality
We and others have documented the strong 
relation between DvC and substance use, as 
well as the striking lack  of relation of sub -