64 I. THEORETICAL  PERSPECTI vES AND  CONCEPT uAL uNITS
The disadvantage, of course, is their low 
fidelity. In any hierarchical representation, 
one always loses information as one moves 
up the hierarchical levels. For example, 
categorizing something as a “Guppy” is 
more informative than categorizing it as a 
“fish,” which in turn is more informative 
than categorizing it as an “animal.” Or, in 
psychometric terms, one necessarily loses 
item information as one aggregates items 
into scales, and one loses scale information 
as one aggregates scales into factors (John, 
Hampson, & Goldberg, 1991).
The Big Five dimensions represent a 
rather broad level in the hierarchy of per -
sonality descriptors. In that sense, they are 
to personality what the categories “plant” 
and “animal” are to the world of biologi -
cal objects—  extremely useful for some ini -
tial rough distinctions but of less value for 
predicting specific behaviors of a particular 
object. The hierarchical level a researcher se -
lects depends on the descriptive and predic -
tive tasks to be addressed (Hampson et al., 
1986). In principle, the number of specific 
distinctions one can make in the description 
of an individual is infinite, limited only by 
one’s objectives.
Norman, Goldberg, McCrae and Costa, 
and Hogan all recognized that there was a 
need in personality, just as in biology, “to 
have a system in which different levels of gen -
erality or inclusion are recognized” (Simp -
son, 1961, p. 12). A complete trait taxonomy 
must include middle-  level categories, such as 
Assertiveness, Organization, and Creative 
Imagination (e.g., John, Hampson, & Gold -
berg, 1991). Costa and McCrae’s (1992) 30 
facets represent the most widely used and 
empirically validated model. The 10 aspects 
in the BFAS (DeYoung et al., 2007) and the 
more recent 15 facets in the BFI-2 (Soto & 
John, 2017a) have attracted considerable in -
terest in the field, as shown by their citations 
and adaptations into other languages and 
cultures. Hofstee et al.’s (1992) circumplex- 
based AB5C approach defines 45 facets as 
unique, pairwise combinations or “blends” 
of the Big Five factors (e.g., Poise as a blend 
of high Extraversion and low Neuroticism); 
measures of these facets have now been de -
veloped as a part of Goldberg’s collaborative 
and web-based International Personality 
Item Pool (IPIP) project. Saucier and Osten -dorf (1999) provided a thoughtful discus -
sion of the fundamental issues in developing 
empirically based facets and presented 18 
facets that show some cross-  language gener -
alizability. Table 2.3 shows some promising 
convergences, but the number and nature of 
the facets proposed so far still varies tremen -
dously, indicating that further conceptual 
and empirical work is needed to achieve a 
consensual specification of the Big Five fac -
tors at lower level of abstraction.
Person–Environment  Interactions: Do  the Big 
Five Predict Important Life  Outcomes?
Given that the Big Five dimensions were de -
rived initially from analyses of the personal -
ity lexicon, one might wonder whether they 
merely represent linguistic artifacts. Do the 
Big Five actually predict important behavior -
al and life outcomes in people’s lives? Initial -
ly, external validity and predictive utility did 
not receive much attention from researchers 
working in the Big Five tradition. Indeed, 
Eysenck (1991, p. 785) challenged the field, 
arguing that “little is known about the so -
cial relevance and importance of openness, 
agreeableness, and conscientiousness. . . . 
What is lacking is a series of large-scale 
studies which would flesh out such possibili -
ties.” Over the past three decades, however, 
researchers have taken up the task of identi -
fying the particular Big Five dimensions that 
predict particular life outcomes in funda -
mental domains such as physical and mental 
health, work, and relationships (see Table 
2.2 for examples). This research is based on 
the assumption that person factors (e.g., the 
individual’s traits) and environmental fac -
tors (e.g., aspects of a job or a relationship 
partner) interact to jointly produce behav -
ioral and experiential outcomes that accu -
mulate over the individual’s life  span (e.g., 
Caspi & Bem, 1990; Scarr & McCartney, 
1983). In other words, personality traits are 
important because they influence the way 
individuals interact with particular environ -
ments. As we review below, traits influence 
how individuals construe and interpret the 
personal meaning a particular environment 
or situation has for them (e.g., how they in -
terpret a potential health risk), and to which 
aspects of the environment they attend (e.g., 
a doctor’s prescribed treatment regimen). In 