KEY WORDS: personality traits. evolution, behavior genetics, biological bases, affect
CONTENTS INTRODUCTION A METATHEORETIC TAXONOMY OF PERSONALITY THEORIES AND PROCESSES: THREE DIMENSIONS OF PERSONALITY THEORY
Levels of Generality--From the Species to the Individual
Levels of Explanation--From the Gene to the Society
Levels of Functioning RECENT TRENDS IN PERSONALITY AND RELATED FIELDS ALL PEOPLE ARE THE SAME: THE STUDY OF SPECIES-TYPICAL BEHAVIOR
Evolutionary Personality Psychology
Evolutionary Causes for Individual Differences
Sociology of Generational Effects
Psychodynamic Theory SOME PEOPLE ARE THE SAME: THE STUDY OF INDIVIDUAL DIFFERENCES AND SIMILARITIES
Trait-Based Differences and Similarities
Situation-Based Differences and Similarities
Trait-by-Situation Interactions NO PERSON IS THE SAME: THE STUDY OF UNIQUE PATTERNS OF BEHAVIOR
Life Histories and the Study of Lives
Life Stones FUTURE DIRECTIONS: CHALLENGES AND PROMISES
The development of psychological theory tends to oscillate between optimistic advances and self-critical analyses and retrenchment. Personality theory is no different. In the past 40 years personality research has seen at least one full cycle of uncritical enthusiasm turn into bleak pessimism and again to enthusiasm. Recent events suggest that the field is again becoming a focal area of psychological study. Exciting discoveries are being made in behavior genetics, there is a growing consensus about the relationship between personality traits and emotional states, biological theorists of adult personality are exchanging ideas with theorists of childhood temperament, and long-term studies of personality development across the life span are delivering on the promises made many years ago. Upon reading the most recent Handbook of Personality (Pervin 1990a) one cannot help being excited by the progress that has been made since the previous edition (Borgatta & Lambert 1968). Many of the tentative findings of the early 1950s (Eysenck 1952, MacKinnon 1951, Sears 1950) have led to substantial contributions that continue to influence our thinking. This claim of a renaissance in personality theory has, however, been made before (Allport & Vernon 193O, Bronfenbrenner 1953, Pervin 1990b). Unfortunately, many promising approaches have led nowhere.
Personality theories attempt to account for individual behavior. The scope of such theories is vast. They describe how genetic predispositions and biological mechanisms combine with experience as children develop into young adults who will show behavioral consistencies over their life spans. Personality researchers report heritability coefficients, relate MRI scans and EEG activity to intellectual performance and emotional reactions, and predict job outcomes and lifetime satisfaction. They examine the dimensions of self-description and the many ways feelings, knowledge, and beliefs combine in behavior. Personality research ranges from tests of evolutionary theories of jealousy to analyses of the structure and content of one's life story.
After 20 years there is a resurgence of interest in the fundamental questions of personality, including 1. What are the relevant dimensions of individual differences in personality? 2. How do genetic mechanisms lead to individual differences? 3. Does personality have a biological basis? 4. How does personality develop? 5. How does personality change? 6. What are the social determinants of personality?
Personality constructs are again being seen in the literature of behavior genetics, cognitive psychology, developmental psychology, evolutionary psychology, physiological psychology, psychopathology, arid social psychology. This review focuses on these related areas partly to clarify their links to personality theory and also to guide those who might be interested in recent advances in personality theory. In addition, it is meant to guide personality researchers to developments reported outside the usual personality journals. Because personality is the study of the whole person, this review focuses on the interrelationships of personality theory with other areas of psychology. Just as other areas of psychology have become more aware of advances in personality, theoreticians within the field must be aware of recent advances in related disciplines.
The earliest reviews of personality were able to address the entire field. Starting with Atkinson (1960), issues of personality dynamics were separated from those of structure and development because it was no longer possible to give adequate coverage in less than book form (if at all). Similarly, this review focuses more on the how and why of personality processes than on the what of personality taxonomy and structure (Digman 1990, Wiggins & Pincus 1992). I consider the metatheoretic question of what is personality and what are the appropriate ways to study it.
A METATHEORETIC TAXONOMY OF PERSONALITY THEORIES AND PROCESSES: THREE DIMENSIONS OF PERSONALITY THEORY
The questions that scientists ask about the world are driven by their scientific metaphors. The chasm between the two disciplines of psychological inquiry so well described by Atkinson (1960), Cronbach (1957, 1975), Eysenck (1966), and Vale & Vale (1969) was a split between two world views, two scientific metaphors, and two data-analytic strategies. The experimentalists emphasized control, manipulation, and the t-test. The individual differences psychologists emphasized adaptation, variation, and the correlation coefficient.
Unfortunately, theoretical and research emphases have splintered beyond even two disciplines. Even within the field of personality there are many different, seemingly unrelated approaches. Current research in personality can be organized along three dimensions: level of generality between people, levels of analysis, and degree of adaptability of the behavior. The first dimension ranges from generalizing to all people to focusing on single individuals and was captured by Kluckhohn & Murray (1948) as emphasizing how all people are the same, some people are the same, and no people are the same. These ways of knowing (McAdams 1994a) can be crossed with a second dimension of analysis, ranging from analyses of the genetic code, through biological mechanisms, learning and developmental processes, and temporary cognitive and emotional structures and processes, to the study of overall life meaning and satisfaction. Phenomena at one level of analysis are only loosely coupled with those at different levels (Figure 1). The third dimension, not shown in the figure, is one of adaptability and functioning. Personality theories need to account for normal adaptive processes as well as extreme psychopathologies. Although broad theories consider issues across these three dimensions, most theorists focus on phenomena that range across levels of analysis at one level of generality, or across levels of generality at one level of explanation.
[Figure 1 ILLUSTRATION OMITTED]
Levels of Generality--From the Species to the Individual
Just as psychology is the study of behavior, personality is the study of individual behavior. Although to many the study of individual behavior has meant the study of individual differences in behavior, an adequate theory of personality process and structure must also account for similarities in behavior. A complete personality theory needs to focus on the three levels of personality identified by Kluckhohn & Murray (1948).
The classical test theory metaphor used by applied and personnel psychologists, and the analysis of variance metaphor used by the interactionists, although compelling, both emphasize sources of variation rather than sources of consistency. Although it is important to consider the interaction of persons and situations as well as the effects of individual and situational differences, by using either a correlational or an analysis of variance metaphor we are unable to ask questions other than how some people are the same and some are different.
A generalization of the analysis of variance metaphor is to consider the other components of the general linear model. Estimates of any particular behavior are expressed in terms of the central tendency across all people, the responsivity to particular situational and person variables, the interaction between the situational and person variables, as well as the reliable within-person variance and that associated with unknown sources of variance.
Theories differ in their central focus as well as in their range of generalizability. Evolutionary personality theory, psychoanalytic theory, behavior theory, and sociology emphasize the commonalities of individual behaviors. Every member of every species needs to meet the challenges of survival and of reproduction. How these challenges are met within a species reflects species-typical solutions. By understanding how these problems are answered by humans as a species we can understand the fundamentals of human nature. Trait theorists focus on systematic individual differences and similarities among people. Although some emphasize how general laws lead to behavioral differences (Eysenck 1990), at the extreme, this approach consciously shuns universal theories (Hofstee 1991). Social constructionists, phenomenologists, and biographers focus on the unique patterns of a life story after species-typical and broad individual differences and trait influences have been removed (Allport 1962; but see Holt 1962).
Levels of Explanation--From the Gene to the Society
Current research in personality and individual differences ranges from attempts to identify particular genetic sequences associated with behavior to studies of how one's life meaning can be affected by societal changes such as the Depression or a world war. Species-typical behaviors that are the result of genetic selection are proposed by evolutionary psychologists who ask about the origins and reasons for human nature. Behavior geneticists examine the genetic architecture of specific traits as well as the covariances of traits with each other and with different parts of the environment. Behavior genetic analyses also demonstrate within-family and between-family environmental effects. Genes affect particular dimensions of individual differences by modifying biological structures and regulating ongoing processes. Rather than the evolutionary question of why, explanations at the biological level ask how. Although ultimately rooted in biology, cognition, affect, and behavior may be studied independently of biological mechanisms. These are studies of what is human nature. Examining individual differences in behavior in terms of cognitive structures and affective reactions is perhaps the most common personality research. Broad questions of meaning tend to be associated with philosophically and clinically oriented theorists who emphasize how people organize their lives in terms of recurrent themes and problems. Research on the effect of the self-concept, self-esteem, career choice, personality disorders, satisfaction, and development throughout the life span also emphasizes this highest level of analysis.
Levels of Functioning
Personality theories are not just theories of normal functioning. They also address dysfunctional as well as high-level behavior. Although many limit their studies to unselected groups of adolescents and adults, others examine selected groups such as prisoners, patients, and professionals.
RECENT TRENDS IN PERSONALITY AND RELATED FIELDS
Recent Annual Review of Psychology chapters on personality theory and research reflect the breadth and scope of the field. Buss (1991) proposed that evolutionary theory provides the necessary framework for the study of personality. Evolutionary personality theory addresses the goals and mechanisms to achieve them that are typical of our species. It also focuses on individual strategies that are used to meet species-typical challenges. Magnusson & Torestad (1993) evoked biological models and systems theory to emphasize the need to consider dynamic processes of cognitive construals as active, purposeful agents interact with their world. Digman (1990) reviewed the consistent findings in personality taxonomic work and reported strong agreement across different research groups on the number and identification of the basic dimensions of personality. Wiggins & Pincus (1992) elaborated on structural questions of the assessment of basic dimensions and concluded that there is strong agreement on personality structure from those examining enduring disposition, dyadic-interactions, social competencies, or natural language. Ozer & Reise (1994) shared that view and emphasized methodological rather than substantive issues in personality assessment.
Even with the diversity of perspectives seen in the above chapters, personality theory is too broad to be included in a single review. A complete review of personality processes needs to include recent social psychology advances in self-theory and social cognition, cross-cultural sources of variation, biological theories of memory structure, and techniques of brain imaging. Theoretical advances in the biological nature of schizophrenia and the affective disorders shed light on both normal and psychopathological functioning. Techniques of treatment of the anxiety disorders are relevant to theories of normal personality. These topics and more have appeared in recent issues of the Annual Review of Psychology.
In addition, there has been a proliferation of "handbooks" devoted to various aspects of personality. For an overview of the field, the Handbook of Personality Theory (Pervin 1990a) is essential reading. Gale & Eysenck (1992) review advances in biological approaches. Smith & Jones (1992) review individual differences in trait and states as they affect human performance. Conferences and edited volumes sponsored by the American Psychological Association have emphasized longitudinal research (Funder et al 1993, Heatherton & Weinberger 1994), temperament (Bates & Wachs 1994), and the application of personality assessment to psychopathology (Costa & Widiger 1994). Special issues of the Journal of Personality have been devoted to long-term stability and change in personality (West & Graziano 1989), the biological foundations of personality (Buss 1990), personality and daily experience (Tennen et al 1991), the five-factor model (McCrae 1992), and personality judgment (Funder & West 1993). Special issues of Cognition and Emotion particularly relevant to personality processes have addressed the psychobiological aspects of relationships between emotion and cognition (Gray 1990, Watts 1993), the question of whether there are basic emotions (Stein & Oatley 1992), and the role that cognitive appraisals play in emotion (Frijda 1993).
ALL PEOPLE ARE THE SAME: THE STUDY OF SPECIES-TYPICAL BEHAVIOR
It is easy to forget, when considering human behavior, how similar we all are to each other. Demonstrations of this similarity include the compelling "Barnum effect" observed when judging the …