The Hierarchical Structure of Personality 67recently, it was unclear whether the lower-order traits were
merely facets of the higher-order traits or distinct entities
with their own etiology. The use of the termfacetto de-
scribe the lower-order traits, a convention adopted by Costa
and McCrae, implies that they are merely exemplars or
components of a more fundamental global trait. In this
sense, the facet traits can be understood in terms of the do-
main sampling approach used in test construction in which
facets are merely arbitrary ways to subdivide global traits
to ensure adequate domain sampling. Identification of gen-
eral genetic factors that have a broad influence on personal-
ity phenotypes also raises questions about the significance
of the lower-order or facet traits—in particular, whether
these traits are heritable simply because of their association
with the broader domains or whether they are also subject to
specific genetic influences. Clarification of this issue is crit-
ical to constructing an explanatory account of personality
structure.
Heritability of Lower-Order Traits
If lower-order traits are only subcomponents of broader traits,
all variance in a facet apart from error variance should be ex-
plained by the variance in the global trait. Recently, however,
behavioral genetic research has suggested that lower-order
traits have a distinct heritable component (Jang et al., 1998;
Livesley et al., 1998). These studies estimated whether lower-
order traits have a unique genetic basis when the heritable
component of higher-order traits is removed from them. Jang
and colleagues (1998) partialled out all of the common vari-
ance due to each of higher-order Neuroticism, Extraversion,
Openness, Agreeableness, and Conscientiousness scales from
the 30 facet scales of the NEO-PI-R. When the residual vari-
ances on the facets were subjected to heritability analyses, a
substantial genetic influence remained. Additive genetic ef-
fects accounted for 25 to 65% of the reliable specific variance,
with most heritabilities ranging from .20 to .35 (see Table 3.3).
When these values were corrected for unreliability, the
values increased to the usual range observed for personality
traits. The implication is that these traits are not merely facets
of more general traits, but rather distinct heritable entities.
A similar approach was used to study the residual heri-
tability of the 18 traits underlying personality disorder
(Livesley et al., 1998). Factor scores were computed for the
four factors described previously. A standardized residual
score for each scale was computed by regressing the four fac-
tor scores on each of the 18 basic traits. Monozygotic twin
correlations were higher that the dizygotic twin correlations
for all 18 traits. Estimates of the heritability of the residual
trait scores showed substantial residual heritability for 11 of
TABLE 3.3 Heritability Estimates, Retest Reliabilities, and
Relative Reliabilities of Revised NEO Personality Inventory Residual
Facet Scores
Domain and Facet Scale h^2 c^2 e^2 ru h^2 /ru
Neuroticism
Anxiety 0.25 — 0.75 0.58 0.43
Hostility 0.21 — 0.79 0.53 0.40
Depression 0.25 — 0.75 0.50 0.50
Self-Consciousness 0.29 — 0.71 0.54 0.54
Impulsiveness 0.27 — 0.73 0.59 0.46
Vulnerability 0.26 — 0.74 0.56 0.46
Extraversion
Warmth 0.23 — 0.77 0.60 0.38
Gregariousness 0.28 — 0.72 0.71 0.39
Assertiveness 0.29 — 0.71 0.72 0.40
Activity 0.27 — 0.73 0.70 0.39
Excitement Seeking 0.36 — 0.64 0.69 0.52
Positive Emotions 0.30 — 0.70 0.63 0.48
Openness
Fantasy 0.25 — 0.75 0.60 0.42
Aesthetics 0.37 — 0.63 0.72 0.51
Feelings 0.26 — 0.74 0.57 0.46
Actions 0.34 — 0.66 0.69 0.49
Ideas 0.33 — 0.67 0.69 0.48
Values 0.35 — 0.65 0.71 0.49
Agreeableness
Trust 0.31 — 0.69 0.62 0.50
Straightforwardness 0.25 — 0.75 0.56 0.45
Altuism — 0.20 0.80 0.50 —
Compliance 0.26 — 0.74 0.54 0.48
Modesty — 0.26 0.74 0.64 —
Tendermindedness 0.28 — 0.72 0.64 0.44
Conscientiousness
Competence 0.11 — 0.89 0.44 0.25
Order 0.26 — 0.74 0.69 0.38
Dutifulness 0.28 — 0.72 0.43 0.65
Achievement Striving — 0.26 0.74 0.54 —
Self-Discipline 0.28 — 0.72 0.61 0.46
Deliberation — 0.18 0.82 0.71 —the 18 basic traits that ranged from .26 for Intimacy Prob-
lems to .48 for Conduct Problems.
These studies, in contrast to studies of phenotypic struc-
ture, point to the significance of the lower-order traits.
Although these traits have tended to be neglected in personal-
ity research, they appear to be important for understanding
personality. This suggests that a bottom-up approach to per-
sonality structure would provide additional information to
complement that provided by the traditional top-down
approach of the three- and five-factor models that identify the
higher-order domains first and then seek to define an appro-
priate complement of facet traits. Before considering these is-
sues in greater depth, it is important to recognize a limitation
of the methods used. The regression method does not model
genetic effects directly, and the results need to be replicated
using multivariate genetic analyses. This introduces another
feature of behavioral genetic analyses that is pertinent to