Chapter Outlines
This book is about individual differences, which is the study of the major aspects by, and reasons why, people differ. At the same time, individual differences can help us explain why certain people are alike. Thus, the study of individual differences attempts to provide the psychological units of measurement to describe similarities and differences between individuals' patterns of thought, emotion, and behavior. As such, it is quite different from other areas of psychology, which are concerned primarily - and sometimes exclusively - with the psychological processes that characterize human behavior in general. Whilst the core aspects of psychological processes, such as memory, attention, perception and learning are ubiquitous to the human species, individual differences such as personality, intelligence, and motivation explain why two people picked at random will only be superficially similar in any of those, or any other, psychological variables, just as two people picked at random are unlikely to have exactly the same height or weight. But why are people different, and how exactly do we differ from each other? Are the causes of individual differences more inherited or learned? Can we change the way we think and feel about everyday aspects of life or is our behavior pre-determined (e.g., imprinted or encoded in our genes)? What role do our personality and intelligence play in everyday life? Are personality and intelligence the same or different things? What makes a person more authoritarian? Why are certain people brighter or more creative than others? What makes us like certain people but dislike others? Can we learn to become more intelligent? What inspires people to become leaders, and why are some leaders more successful than others? These are some of the questions guiding this book.
Chapter 1 is an introduction to the book. Starting with simple questions about personality and individual differences, I introduce the major topics of differential psychology, each of which will be the focus of the book's chapters. The idea of this chapter is therefore to link topics such as intelligence, personality and creativity to everyday questions and psychological observations that are common to both laypeople and scientific experts in these areas.
Chapter 2 introduces one of the two major topics of individual difference research, namely the construct of personality traits. Starting with a historical overview of the preliminary developments of "temperament" classification by the ancient Greeks, this chapter examines the transition from pre-scientific to modern psychometric approaches, with particular emphasis on the notion of personality "types" and "traits". Main theories include Eysenck's Giant Three and Costa and McCrae's Big Five (the five factor model).
Chapter 3 looks at personality traits in the real world. Thus, it differs from chapter 2 (which was mainly designed to explore the structure of personality) in that it attempt to assess the "validity" of personality as predictors of a wide range of behaviors, from academic performance to interpersonal relations and happiness. To this end, I introduce some basic statistical notions, such as correlations and regressions, which are fundamental to understand research into personality traits as well as most individual difference variables.
Chapter 4 explores issues surrounding the difference between normal and abnormal behavior, thus introducing the topic of psychopathology or psychiatric disorders. Whilst many individual difference researchers focus on normal rather than abnormal behavior, I show in this chapter that the distinction between normality and abnormality is merely conceptual (and often elusive). Furthermore, whilst there has been widespread agreement as to how we should classify the basic forms of pathology or mental illness (e.g., schizophrenia, anxiety disorder, depression, etc.), there is a lack of theoretical frameworks to understand the exact causes and consequences of such forms of behavior. Recent and current trends suggest that normality (personality) and abnormality (psychological disorders) are not essentially different, but share the same structure and are linked via the same evolutionary mechanisms.
Chapter 5 introduces the topic of intelligence, which, together with personality, represents the essence of differential psychology. In fact, individual differences as a scientific discipline and sub-branch of psychology was pretty much initiated with the study of intelligence or cognitive abilities, a tradition that begun in Britain more than one hundred years ago. In this chapter I introduce the main theories of intelligence and discuss the salient issues about the structure (how many abilities are there?), measurement (different ability tests) and implications (what does it mean to be more intelligent and what does it mean to score higher or lower in an IQ test?) of intellectual ability.
Chapter 6 is concerned with the causes and consequences of intelligence; as such, it follows up on chapter 5. In this chapter I discuss some of the most controversial issues revolving around the concept of IQ, such as the question of group (gender and race) differences, whether intelligence is mainly inherited or acquired (genetic vs. environmental approaches), and whether higher intellectual ability offers any real advantages in everyday life. Whilst there is heated debate about these questions, particularly by the media and along the lines of popular and political discussions, there is sufficient empirical evidence to assess these issues in a rather objective manner, though of course research is far from being conclusive.
Chapter 7 looks at the causes of personality and intelligence, the major individual difference constructs. In particular, it is concerned with the study of behavior genetics, which is the area of psychology that estimates the extent to which behaviors can be attributed to biological (genetic) or environmental (non-genetic) factors. This is an old question which precedes the study of psychology and has concerned philosophers for thousands of years. In psychology, however, this area has received widespread attention since the identification of major twin-, family-, and adoptive- databases has enabled researchers to quantify the magnitude of both genetic and non-genetic influences on personality and intelligence.
Chapter 8 deals with novel or "hot" intelligences, which are conceptualizations of human ability that depart from the traditional notion of IQ. Instead, hot intelligences (e.g., emotional, social, and practical intelligence) attempt to expand our understanding and measurement of abilities to account for an array of non-academic competences. For example, people may score low on traditional IQ tests (because they are not particularly good at solving mathematical, spatial, or logical problems) and nevertheless be "experts" in interpersonal relations or very "bright" at managing their own and others' emotions. Whilst this idea is intuitively appealing (as evidenced by the best-selling books by Gardner and Goleman), it has yet to be supported by real scientific evidence and, in most cases, is in direct contradiction with established findings.
Chapter 9 examines the topics of mood and motivation, which have represented important concepts and a longstanding research tradition in differential psychology for decades. The study of mood refers to individual differences in emotionality and its central concept is affect. Noteworthy is, that there is both within- and between-individuals variability in affect, meaning we do not always experience the same feelings or emotions, though different people will differ in the extent and type of emotions they tend to experience most of the times. Motivation on the other hand explains what drives us to behave in different ways and comprises a variety of broad and classic theories, from biological to existential, of human behavior.
Chapter 10 is concerned with the study of creativity. Though not a novel area, creativity has recently been the focus of a growing number of studies in differential psychology, particularly in relation to personality, intelligence and psychopathology. One of the problems with creativity research is that the concept means different things in different contexts, and that a variety of approaches exist (and have simultaneously existed, though unfortunately usually in isolation) for the study of creativity. Yet there is increasing agreement that creativity deserves a unique chapter in differential psychology and that, even if it is related to established personality and ability traits, it cannot be completely explained by other individual difference variables.
Chapter 11 looks at the concept of leadership and how it has been investigated in the tradition of differential psychology. Like creativity, leadership is both a trait and a process, and depends largely, though not exclusively, on other individual difference factors such as personality and intelligence. Thus leaders tend to be bright, charismatic, extraverted, and conscientious, though such factors alone (even when combined) are insufficient to predict who will become a leader, let alone a successful one. Thus situational and personal factors interact to determine individual differences in leadership, and the challenge - not only for differential psychology - is to increase our understanding into the causes and consequences of different leadership styles, as well as improve our methods for assessing and measuring leadership.
Chapter 12 explores the final topic of this book, namely vocational interests. Although, together with personality and intelligence, interests have represented one of the salient components of differential psychology for decades, it is only in recent years that individual difference researchers have attempted to incorporate the construct of interests in the wider context of personality and intelligence. Some of the most fascinating advances in the field of differential psychology are in fact the result of examining the relationship between personality, intelligence, and interests, more specifically how ability and non-ability traits interact to determine specific vocational interests, and how these, in turn, feed back onto the development of skill acquisition and adult individual differences.