CHAPTER 3
Genetic Basis of Personality Structure
W. JOHN LIVESLEY, KERRY L. JANG, AND PHILIP A. VERNON
59DOMAIN DEFINITION: UNRESOLVED PROBLEMS WITH
PHENOTYPIC STRUCTURE 60
Number of Domains 60
Domain Definition 60
Approaches to Domain Definition 61
HERITABILITY 62
THE ETIOLOGICAL BASIS OF COVARIANCE 63
PHENOTYPIC STRUCTURE AND GENETIC ARCHITECTURE
OF PERSONALITY 64
THE HIERARCHICAL STRUCTURE OF PERSONALITY 66
Heritability of Lower-Order Traits 67
Independent and Common Pathways Models 68
Five-Factor Model 69
Personality Disorder Traits 70
IMPLICATIONS FOR PERSONALITY STRUCTURE 70
Hierarchical Structure 71
Basic-Level Traits: Defining the Basic Unit
of Personality 72
Domain Content 73
UNIVERSALITY OF TRAIT STRUCTURE 73
Cross-Cultural Comparisons 73
Gender Differences 74
ENVIRONMENTAL EFFECTS 76
MOLECULAR GENETICS 77
CONCLUSIONS 78
REFERENCES 79Until recently, the study of personality was handicapped
by the lack of a systematic taxonomy of constructs to repre-
sent individual differences. A confusing array of con-
structs and measures was available, and different measures of
purportedly the same construct often showed little correspon-
dence. This diversity hindered the development of a system-
atic understanding of individual differences. Recently, the
situation began to change with emerging agreement about
some of the major dimensions of personality. Broad traits
such as neuroticism-stability, extraversion-introversion, and
psychoticism-constraint are identified in most analyses of
personality traits and part of most descriptive systems. There
is also agreement about the way personality is organized.
Models based on trait concepts assume that traits differ along
a dimension of breadth or generalization and that traits are hi-
erarchically organized, with global traits such as neuroticism
subdividing into a set of more specific traits such as anxious-
ness and dependence (Goldberg, 1993; Hampson, John, &
Goldberg, 1986).
Within this framework, attention has focused particularly
on the five major factors as a parsimonious taxonomy of per-
sonality traits (Goldberg, 1990). Lexical analyses of the nat-
ural language of personality description (Digman, 1990;
Goldberg, 1990) and subsequent psychometric studies of
personality inventories (Costa & McCrae, 1992) have con-
verged in identifying five broad factors typically labeled
extraversion or surgency, agreeableness, conscientiousness,
emotional stability versus neuroticism, and intellect, culture,
or openness. It is widely assumed that this structure is trans-
forming our understanding of personality and that the higher-
order structure of personality is becoming more clearly
delineated. Enthusiasm for the emergent structure, although
understandable because it promises to bring coherence to a
field characterized more by conceptual and theoretical debate
than by substantive findings, tends to minimize confusions
that still exist regarding the number and content of higher-
order domains (Zuckerman, 1991, 1995, 1999; Zuckerman,
Kulhman, Joireman, Teta, & Kraft, 1993) and nature of the
assumed hierarchical arrangement of traits.
These problems remain unresolved despite numerous
attempts to explicate personality structure, partly because the
methods used incorporate subjective elements regarding
choice of analytic strategies and data interpretation, and
partly because personality concepts are inherently fuzzy, a
factor that contributes to interpretive problems. In this chap-
ter, we examine the contribution that behavioral genetic
approaches can make to explicating the structure of personal-
ity and resolving issues of the number and content of