How do we come to be who we are? Why do we differ in our personalities? How do these differences matter in life? Individual Differences and Personality aims to describe how and why personality varies among people. Unlike books that focus on individual theorists, this book focuses on current research and theory on the nature of personality and related individual differences. The book begins by discussing how personality is measured, the concept of a personality trait, and the basic dimensions of personality. This leads to a discussion of the origins of personality, with descriptions of its developmental course, its biological causes, its genetic and environmental influences, and its evolutionary function. The concept of a personality disorder is then described, followed by a discussion of the influence of personality on life outcomes in relationships, work, and health. Finally, the book examines the important differences between individuals in the realms of mental abilities, of beliefs and attitudes, and of behavior.

Key Features

  • Presents a scientific approach to personality and related individual differences, as well as theory and research on the fundamental questions about human psychological variation
  • New edition presents findings from dozens of new research studies of the past six years
  • Includes new chapter on vocational interests and a revised chapter on personality disorders reflecting DSM-5 formulation
  • Contains streamlined descriptions of measurement concepts and heritability research
  • Includes various boxes containing interesting asides that help to maintain the student’s attention.


Undergraduate and graduate level courses in personality.

Table of Contents




The Study of Personality

The Universal, the Unique, and the In-Between

Idiographic Versus Nomothetic Approaches

Outline of this Book

Chapter 1. Basic Concepts in Psychological Measurement

1.1 Some Simple Statistical Ideas

1.2 Assessing Quality of Measurement: Reliability and Validity

1.3 Methods of Measurement: Self- and Observer Reports, Direct Observations, Biodata

1.4 Summary and Conclusions

Chapter 2. Personality Traits and the Inventories that Measure Them

2.1 The Idea of a Personality Trait

2.2 Personality Traits and Other Psychological Characteristics

2.3 Do Personality Traits Exist?

2.4 Measuring Traits by Self- or Observer Report: Structured Personality Inventories

2.5 Strategies of Personality Inventory Construction

2.6 Self- and Observer Reports on Personality Inventory Scales

2.7 Summary and Conclusions

Chapter 3. Personality Structure: Classifying Traits

3.1 Which Traits to Measure? Completeness without Redundancy

3.2 A Gentle Introduction to Factor Analysis

3.3 Factor Analysis of Personality Traits: How to Find a Representative Set of Traits?

3.4 Lexical Studies in the English Language: The Big Five Personality Factors

3.5 Lexical Studies in Many Languages: The HEXACO Personality Factors

3.6 What it all Means: A Few Dimensions, but Many Personalities

3.7 Summary and Conclusions

Chapter 4. Developmental Change and Stability of Personality

4.1 Defining Change and Stability

4.2 Developmental Changes in Mean Levels of Personality Traits

4.3 Stability of Traits Across the Years (and the Life Span)

4.4 Personality in Childhood and Infancy: Measurement and Structure

4.5 Summary and Conclusions

Chapter 5. Biological Bases of Personality

5.1 Early


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Academic Press
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"Ashton presents this text on personality development, assessment, and pathology… A wide variety of measurement instruments and theoretical frameworks are presented, often accompanied by illustrative diagrams or placed in supplementary text-boxes." --Reference & Research Book News, 2013