As we have seen in Chapters 3, 4, and 5, German psychologists concentrated on the experimental study of human behavior and thought processes and gave little attention to comparative psychology. Nineteenth-century British psychologists, in contrast, concentrated on comparative study and were little concerned with experimental studies of human psychology. The combination of the two approaches, which forms the basis for present-day psychology, was the achievement of American psychologists.

Comparative psychology had a promising beginning after Darwin's and Wallace's formulation of the theory of evolution, but by around 1900 interest in it had evaporated in Great Britain. Still, the comparative study of psychology continued in Continental Europe and the United States. In Europe, it was carried on by zoologists as a study of behavior, which they named ethology. Their research remained largely unknown to psychologists until about 1950. In the United States, during the first half of the twentieth century, psychologists approached the study of behavior differently. Whereas the Europeans concentrated on perception and genetic factors, the Americans studied ontogenetic development and emphasized the importance of learning. A confrontation arose, leading to an open academic debate that Robert Hinde (1995) has described as being productive for the development of psychology. I shall return to this confrontation in Chapter 19 and link ethology more closely to psychology; here, I shall merely note the connection between them.

The British comparative psychologists were particularly concerned with the following two problems: the relationship between the intellectual capacities of animals and humans, and the question of whether animals and humans possess instincts. With regard to the latter problem, the discussion revolved primarily around whether any forms of behavior could be regarded as innate. However, at the beginning of the twentieth century, researchers also asked whether behavior is elicited not only by direct outer stimulation but also by an inner state. This question became central in the study of motivation and personality. To gain a perspective on the study of motivation, we will view it in the context of the debate on instincts. These two problems that interested the early British comparative psychologists are related, but at the same time so different that I think it is appropriate to give each of them a separate treatment.

We saw in Chapter 7 that William McDougall attempted to base a social psychology on his ideas of human instincts, but that this attempt did not lead to a more lasting research tradition. George Mead, in contrast, succeeded in establishing a research tradition for the study of social phenomena, as shown in Chapter 11. But this tradition developed within sociology, not within psychology. Not until the 1920s–1930s did psychologists begin to organize a study of social psychology, or that branch of psychology dealing with social interactions, particularly regarding their origins and effects on individual behavior. However, it was not until the 1950s in the United States that they succeeded in establishing social psychology as a formal subdiscipline of psychology.

One important motive for extending psychology to include the study of social phenomena was a desire among psychologists to contribute to the solution of political and social issues by means of empirical research. In a historical introduction to the study of social psychology, Gordon Allport (1954) elaborated this motive by pointing out that there was a tradition in the United States of solving practical problems through empirical research and new technology. Following World War I, race riots; the Great Depression; the high rate of unemployment; the establishment of communist, Nazi, and fascist regimes in Europe; the outbreak ofWorldWar II; and the genocide of the Jews created numerous pressing political and social issues. According to Allport, these inspired US social scientists to contribute to solutions. The result, as he showed, was a flowering in the social sciences.

Social psychology as the study of our social nature has close ties to sociology, political science, and cultural anthropology. The division of labor among the four disciplines raises intricate questions that tend to be answered differently by the researchers in each. The disagreement between sociologists and psychologists about their respective roles has been clearly manifested in the existence, from the beginning of the 1920s to the present, of two social psychologies, one forming part of psychology and one forming part of sociology. To achieve a deeper understanding of what social psychology is about, it is useful to reflect a little on this fact, and I shall begin the chapter by commenting on the relationship between the two social psychologies.

The study of personality arising in the United States in the 1920s and 1930s was an attempt to fuse together a number of diverse traditions, chief among which were the study of individual differences originating with Galton and the clinical study of personality begun by Freud, Jung, Adler, and their students. The European clinical psychologists had aimed to account for personality as a whole and had made it a central concept in explaining motivation. Thus, the US study, as Dan McAdams (1997) recounts, attempted to understand: 1. personality as a whole, 2. motivation, and 3. individual differences.

Wundt and the early German experimental psychologists were interested in characteristics human beings have in common; as Boring (1929/1950) noted, they studied the average adult human being. Galton had understood the role differences between individuals play in evolution, and this was his primary reason to begin the study of individual differences. The pioneers in the US study of personality were not particularly interested in the theory of evolution but were keenly interested in individuality. This focus helps explain why the study of personality became a major focus of inquiry of psychology in the United States (David Winter and Nicole Barenbaum,1999).

The emphasis on individual differences also made the US study different from earlier European work based on clinical psychology. Further, US psychologists were interested in applying the study to the selection of applicants for particular jobs in business, industry, and the military, and came to base their studies on tests and psychometric measurement. Those interested in characteristics of personality were inspired by Galton's measurements and Binet's intelligence test, and by the 1920s they had developed questionnaires and rating scales into useful instruments. When more extensive approaches were presented at the end of the 1930s, the ground had been prepared for more than a decade. This gave the study an orientation towards objective methods from the start.

Naturally, a concept covering such disparate phenomena as personality as a whole, motivation, and individual differences is not easily defined, and the editors of two comprehensive handbooks of personality (Robert Hogan et al., 1997; Lawrence Pervin and Oliver John, 1999) did not give their contributors a definition that could serve as a guideline for them or for readers.