Handbook of Psychology, Volume 5, Personality and Social Psychology

The Hierarchical Structure of Personality 69

Common Pathways Model

G
 additive genetic effects common to all variables

E 
 nonshared environmental effects common to all variables

g 
 additive genetic effects unique to each variable

e 
 nonshared environmental effects unique to each variables

G E

Anxiety Hostility Depression Self-conscious Impulsivity Vulnerability

g e g e g e g e g e g e

NEUROTICISM

Figure 3.2 Common pathways model; G =additive genetic effects common to all variables, E =non-

shared environmental effects common to all variables, g =additive genetic effects unique to each vari-

able, and e =nonshared environmental effects unique to each variable.

hierarchy. If the independent pathways model provides the
best fit, however, the implication is that the higher-order con-
structs of phenotypic analyses do not reflect the effects of a
phenotypic entity, but rather the pleiotropic action of the
genes shared by all lower-order or facet traits that define
the domain. Under these circumstances, the task is to expli-
cate the mechanisms that lead to trait clusters. Regardless of
which model provides the best fit to the data, a useful feature
of both models is that the magnitude of the path coefficients
between each facet scale and the common genetic factor or
latent variable along with information on the magnitude of
genetic and environmental influences unique to each facet
provides the basis for determining which facets should be
grouped together within the taxonomy.

Five-Factor Model

Jang and colleagues (in press) fit common and independent
pathways models to evaluate the coherence of the five do-
mains assessed with the NEO-PI-R. The models were applied
separately to a sample of 253 identical and 207 fraternal
twin pairs from Canada and 526 identical and 269 fraternal
pairs from Germany. The two samples made it possible to
examine the universality of the etiological basis for personal-
ity structure by investigating whether the same genetic and

environmental factors influenced personality traits in the two

samples and whether they had similar effects.

For each sample, a single-factor common pathways

model and a series of independent pathway models specify-

ing variable numbers of genetic and nonshared environmen-

tal factor were fit to the six facets defining each domain.

Shared environmental effects were omitted from the models

because their effects were minimal. For each domain, the

best fit was obtained with an independent pathways model.

Table 3.4 illustrates the findings for the Neuroticism do-

main. An independent pathways model specifying two ge-

netic factors and two nonshared environmental factors

provided the most satisfactory explanation of the covariance

between the six Neuroticism facets in the two samples. In

both samples, the first genetic factor was marked by the

Angry Hostility facet and, to a lesser extent, Anxiety. The

second factor influenced all facets except Angry Hostility

and Impulsivity. The depression facet had the highest load-

ing in both samples.

In addition to demonstrating that the independent path-

ways model provided the best fit, these findings also suggest

that the broad domains of personality are nonhomogeneous.

This raises important questions about the factors that account

for the apparent hierarchical structure of personality traits

and the nature and conceptual status of the higher-order