60 Genetic Basis of Personality Structure
domains. The argument we advance is that an approach that
contributes to understanding of the causesof trait covariation
(as opposed to approaches that simply offer descriptionsof
trait covariation) offer an important perspective on these
intractable taxonomic problems.
DOMAIN DEFINITION: UNRESOLVED PROBLEMS
WITH PHENOTYPIC STRUCTURE
Number of Domains
Despite the dominance of the five-factor approach, disagree-
ment still exists on the number of dimensions required to
represent the higher-order structure of personality. Almagor,
Tellegen, and Waller (1995), for example, suggested that
five factors do not capture all dimensions of the natural lan-
guage of personality because lexical analyses excluded terms
that were evaluative or described temporary states such as
mood. When they used an unrestricted set of terms, seven
factors were identified. Five factors—Positive Emotionality,
Negative Emotionality, Dependability, Agreeableness, Nega-
tive Emotionality, and Conscientiousness—corresponded to
the five-factor dimensions of Extraversion, Neuroticism,
Conscientiousness, Agreeableness, and Openness (nega-
tively), respectively. The remaining factors were evaluative
dimensions, Positive Valence and Negative Valence, which
are not represented in the five-factor model. They concluded
that the seven-factor model provides a better representation
of lexical descriptions of personality. McCrae and John
(1992) and Widiger (1993) refuted this conclusion, claiming
that positive and negative valence factors could be assumed
under the five factors.
Whereas Almagor, Tellegen, and Waller (1995) main-
tained that the five-factor model is too parsimonious, Eysenck
(1991) suggested that it is not parsimonious enough. He ar-
gued that the five domains differ in abstractness and that the
five dimensions could be accommodated within his three-
factor model of Psychoticism, Extraversion, and Neuroticism
because the Openness and Agreeableness domains are merely
facets of Psychoticism. Studies examining the relationship
between NEO-PI-R (Neurosis Extraversion Openness-
Personality Inventory-Revised) and EPQ-R (Eysenck Person-
ality Questionnaire-Revised), however, suggest that although
the two scales overlap they assess unique aspects of personal-
ity (Avia et al., 1995; Draycott & Kline, 1995). These prob-
lems occur because the five factors, although assumed to be
orthogonal, in fact intercorrelate. For example, correlations
between NEO-PI-R Neuroticism and Conscientiousness
domains and Extraversion and Openness to Experience do-
mains are−.53 and .40 respectively (Costa & McCrae, 1992).
These values raise the important issue of what degree of over-
lap or covariation between domains is tolerable. Whether
these values are interpreted as unimportant or substantial de-
pends largely on the investigator’s theoretical perspective.Domain DefinitionA related issue is lack of agreement on the lower-order traits
that define each domain. Identification of an optimal set of
lower-order traits has proved difficult (Costa & McCrae,
1998). Questions about whether a facet belongs to a proposed
domain are raised when it consistently correlates with facets
comprising another domain. For example, although Costa
and McCrae (1992) report a moderate correlation of −.25
between total domain scores for Neuroticism and Agreeable-
ness, the correlations between the Neuroticism facet Angry
Hostility and Agreeableness facets Trust, Altruism, and Com-
pliance are −.42,−.34, and −.49, respectively, and the cor-
relation between Angry Hostility and the total Agreeableness
domain score is −.47. Similarly, the correlation between the
total Neuroticism domain score and the Agreeableness facet
Trust is −.37. How this overlap is interpreted often forms the
basis of many authors’ claims as to why their model provides
the “correct” description of personality. As with the intercor-
relations among domains, the interpretations placed on the
findings are largely arbitrary.
This problem is also revealed by factor analyses of facet
scales. Although factor loadings may conform to simple
structure and the hypothesized five-factor pattern, some facets
may have an appreciably lower loading than do the other
facets defining a domain. This occurs with the NEO-PI-R
Neuroticism facet of Impulsiveness. The correlations be-
tween Impulsiveness and the other Neuroticism facets range
from .31 to .40 (Costa & McCrae, 1992). The median inter-
correlation is .35, whereas the median intercorrelation among
the other facets is .57. Findings such as these raise questions
about the definition of domains and the possibility that addi-
tional domains are required to provide a comprehensive
taxonomy.
The issue of establishing a coherent set of traits for each
domain is related to the interpretation of each domain. Even
within the five-factor approach there are differences in the in-
terpretation of some domains, especially the domain that
Costa and McCrae label Openness to Experience. They em-
phasize such defining characteristics as artistic, curious, orig-
inal, and having wide interests (McCrae & Costa, 1985a,
1985b). In the NEO-PI-R, the factor is defined by ideas