Individual Differences and Personality
Edited by Sarah E. Hampson and Andrew M. Colman
1995, London and New York: Longman. Pp. xiv + 112. ISBN 0-582-27806-6
Notes on editors and contributors
Series editor's preface
1 Intelligence and Cognitive Styles
Robert J. Sternberg Yale University, USA
2 The Construction of Personality
Sarah E. Hampson Oregon Research Institute, USA
3 Trait Theories of Personality
H. J. Eysenck University of London Institute of Psychiatry, England
4 Freudian Theories of Personality
Richard Stevens The Open University, England
5 Personality Tests
Paul Kline University of Exeter, England
Sarah E. Hampson and Andrew M. Colman
One of the most important ways in which psychology
differs from the natural sciences arises from the existence of individual
differences. Two litres of hydrogen that are treated identically respond
identically, but any two human beings, even identical twins, may respond quite
differently to the same stimulus. This is because people differ from one another
not only in appearance (that is, physically) but also in their behaviour (that
is, psychologically). Consequently, the study of individual differences, which
encompasses personality, has been a significant part of psychology since ancient
Frances Galton (1822-1911) is credited with being the first to investigate individual differences scientifically (Galton, 1884). As part of his study of heredity, he developed a large and systematic body of data on individual differences, including both physical and psychological measures. The study of intelligence became the focus of individual-differences research in the first half of the twentieth century. Selection procedures associated with the introduction of universal education, as well as recruitment procedures for two world wars, helped to stimulate demand for measures of individual differences in skills and abilities. As a result, most people nowadays are familiar with the concept of IQ and have experienced intelligence testing of some kind.
Individual differences are not idiosyncrasies. In the study of individual differences, the aim is to identify dimensions that are applicable to everyone but that discriminate among people. For example, everyone is intelligent to some degree. A particular individual's intelligence level can be measured, and that person's intelligence relative to other people's can be determined. In contrast, idiosyncrasies refer to a person's unique characteristics that make him or her different from all other people. The study of individual differences and personality has tended to ignore idiosyncratic characteristics, although one pioneering personality theorist, Gordon W. Allport (1897-1967), included them in his view of personality structure (Allport, 1961).
In some contexts within psychology, individual differences are regarded as "noise". For example, for many purposes it is necessary to treat people as if they were identical, either by selecting a sample whose members all score similarly on relevant dimensions such as IQ, or by having a big enough sample so that effects can be identified against the background of individual variation. However, individual differences are also studied in their own right. In theory, it is possible to study individual differences in any aspect of behaviour. In practice, however, the emphasis of individual-differences research has been upon dimensions related to ways of processing information -- that is, different ways of perceiving and responding to the world (see Gale & Eysenck, 1991).
In chapter 1, Robert J. Sternberg provides an introduction to individual differences and outlines what is known about intelligence and cognitive styles -- people's characteristic ways of thinking. He begins by asking the question, "What is intelligence?" He suggests that one of the ways of answering this question is to ask non-psychologists what they believe intelligence to be. The lay perspective provides a description of intelligence in what is called ordinary language, that is, in terms of everyday descriptions of what differentiates more intelligent from less intelligent individuals. In contrast, psychologists have developed various theories that describe intelligence using scientific concepts to refer to the findings of their research. Sternberg presents several of these theories and approaches. Interestingly, there is considerable overlap between lay and scientific views of intelligence.
Cognitive styles are the characteristic ways in which people make use of their intellectual abilities. Sternberg discusses general or global theories, beginning with Myers's (1980) typology, that identify characteristic styles of thinking that permeate many aspects of the way a person interacts with the world. He also discusses more specific theories that focus on a narrower range of behaviour (for example, the authoritarian style). Cognitive styles are individual differences that lie in a conceptual grey area somewhere between intelligence and personality. It is often difficult (and not of any real importance) to distinguish between what is a personality dimension and what is a cognitive style (Sternberg & Ruzgis, 1994).
The rest of the chapters in this book are concerned with personality. The study of personality is a subset of the study of individual differences. Individuals differ in terms of their personalities in addition to other psychological characteristics such as intelligence and cognitive styles. Personality is usually broadly defined as referring to those internal properties of a person that lead to characteristic patterns of behaviour. Such a broad view of what constitutes personality permits a wide range of approaches. A useful way of organizing the many different theories of personality is to group them into four classes of approach, such as psychodynamic, trait, cognitive-behavioural, and humanistic theories (Peterson, 1992). Each approach reflects different origins and traditions in psychology. In a concise book such as this it is impossible to do justice to the great variety of approaches; but the two most influential, psychodynamic and trait approaches, are presented in some depth.
Richard Stevens's contribution (chapter 4) provides an overview of Freud's contribution to personality theory. Freud remains the most influential and famous of all personality theorists. Indeed, his ideas have indelibly affected the way western culture views human behaviour. Freud developed his ideas over the course of a long career, and Stevens pulls together the various strands of Freud's thinking from different points in time in his presentation of the various sub-theories that make up the body of Freudian theory. These include Freud's views of the unconscious, psychosexual development, and the psychodynamics of personality. Freud's theories have been criticized within psychology for being nonscientific, and Stevens evaluates these criticisms. Despite failing to pass empirical tests, Stevens concludes that Freudian theories have made a lasting contribution by providing a model of an integrative theory in psychology, and by providing an approach to the study of the meaning of behaviour.
Freud's background was in medicine and psychiatry. Many personality theories, including Hans J. Eysenck's trait theory, have their origins in clinical psychology. In chapter 3, Eysenck defends his own influential theory of personality based on three major factors, extraversion, neuroticism, and psychoticism, and discusses it in the light of other trait theories. Traits are defined as relatively enduring characteristics of a person that give rise to stable behaviour patterns. Just as with intelligence, non-psychologists have trait theories of personality too: there is an "ordinary language" of personality description. The three broad traits in Eysenck's theory subsume numerous other lower-level traits familiar to us from lay personality language (for example, extraversion subsumes sociability, liveliness, and activity).
Eysenck's chapter illustrates one point of view on an issue that is hotly debated in personality psychology today. Eysenck argues that only three dimensions or higher-level traits are required to encompass all of personality. Other theorists have argued for many more (for example, Cattell proposed at least sixteen). However, there is a growing consensus that five broad dimensions may be the best the number to capture all aspects of personality (Goldberg, 1993). This issue is discussed further in chapters 2 and 5 by Sarah E. Hampson and Paul Kline.
Regardless of the controversy over the exact number and nature of personality traits, all trait theories depend on the development of reliable and valid measures. In chapter 5, Kline is concerned with personality measurement. He describes the various kinds of personality tests -- self-report questionnaires, projective tests, and objective tests -- and discusses the advantages and disadvantages of each. Both Kline and Eysenck discuss the important issues of reliability and validity of personality measures. Measurement issues are of central importance in the study of individual differences and personality, especially trait theories, because the concepts of interest are not available for direct observation but must inferred indirectly. For example, extraversion is inferred from a person's interpersonal behaviour -- does the person like being around other people? The principles of test construction described by Kline must be employed to ensure that the chosen indicators of an underlying trait are reliable and valid.
Whereas the chapters describing Freudian theories and trait approaches illustrate the connection between personality theories and clinical psychology, in chapter 2 Hampson discusses personality from a social psychological perspective. She views personality as a social construction involving the actor, observer, and self-observer. This view draws on social psychological theories of symbolic interactionism and impression management, as well as sociological theories. The constructivist view of personality provides a framework for integrating a number of related fields. Hampson discusses biological and trait approaches to the study of the actor. The observer of personality has most often been studied as part of social psychology, through research into person perception, and more recently in social cognition. By including the self-observer as part of constructed personality, the study of the self and impression management are also integrated into personality.
The constructivist view provides more than an integrative framework for personality psychology, however. Unlike other approaches to personality, it addresses the relation between the lay perspective -- the "ordinary language" of personality description -- and the scientific perspective. By defining personality in terms of both the actor and the observer, Hampson argues that the meaning and social significance of the actor's behaviour, as understood by both observers and self-observers, are integral parts of personality. Observers and self-observers understand personality in lay terms, and therefore psychologists need to study these lay understandings and relate them to their more scientific investigations. Observers infer personality from behaviour and use personality language to describe their inferences, just as scientists do. Consistent with the legacy of Freudian theories, the study of personality involves the study of the meaning of behaviour.
The chapters in this book represent some of the main approaches to the study of individual differences and personality, and they also address a number of the controversial issues in the field. All the approaches described assume that individual differences remain fairly consistent across time and situations (see chapter 3 by Eysenck), but the possibility of dynamic interactions between situations and persons resulting in personality change is also discussed (see chapter 2 by Hampson). The emphasis on the extent to which personality is inherited and biologically based varies across chapters. Eysenck's trait theory is more biologically based than Freudian theories or social psychological approaches, although all would recognize the importance of inheritance in placing limits on the effects of the environment. The theories represented here are intended to apply to the normal range of personality. Whether or not the same theories can apply to abnormal personality is a matter of debate (see chapters 3 and 4 by Eysenck and Stevens).
Another issue addressed by several chapters is the role of the lay perspective in the scientific study of individual differences. In chapter 1, Sternberg describes his study of lay people's understanding of the concept of intelligence. Hampson (chapter 2), Eysenck (chapter 3), and Kline (chapter 5) all refer to the "Big Five" dimensions of personality. The "Big Five" personality dimensions were originally identified in studies of the ordinary language of personality description. Just as with intelligence, there is considerable convergence between the trait theories based on the non-technical language of personality description and those based on more empirical behavioural observations.
This convergence represents another important difference between the natural sciences and psychology. Some of psychology is concerned with applying scientific methods to study behaviour for which a well-established common-sense psychology already exists. This is the case for the psychology of personality. As social creatures, human beings have developed an extensive vocabulary to describe individual differences. The scientific and lay perspectives on personality are inseparable. Modern physics can tell us that our everyday definitions of light, gravity, or time are wrong, but psychology cannot tell us that our everyday definitions of aggression, anxiety, or altruism are wrong.
We hope that this book will stimulate interest in individual differences and personality. These chapters that follow provide an introduction to some of the most interesting and well researched approaches to the study of individual differences and to some of the dimensions that have been studied. For the reader who wishes to explore a greater variety of approaches and to delve more deeply into the issues in this field, each chapter provides a selection of recommended further reading. The study of individual differences and personality is enjoying a renaissance today as a result of renewed interest in selection processes to match people to situations, but exploring the variety of human nature has always been of enduring fascination.
Allport, G.W. (1961). Pattern and growth in personality. New York: Holt, Rinehart & Winston.
Gale, A., & Eysenck, M. W. (1991). Handbook of individual differences: Biological perspectives. Chichester: Wiley.
Galton, F. (1884). Measurement of character. Fortnightly Review, 36, 179-185.
Goldberg, L. R. (1993). The structure of phenotypic personality traits. American Psychologist, 48, 26-34.
Myers, I. B. (1980). Gifts differing. Palo Alto, CA: Brooks/Cole.
Peterson, C. (1992). Personality. New York: Harcourt Brace Jovanovich.
Sternberg, R. J., & Ruzgis, P. (1994). Personality and intelligence. Cambridge: Cambridge University Press.
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