DIFFERENTIAL PSYCHOLOGY (Individual Differences)

An area of psychology concerned with behavioral differences between individuals and groups of individuals—including, among others, sex, race, nationality, cultural and socioeconomic differences.The importance of individual differences has long been recognized. Anthropological studies show that many positions in preliterate cultures—-the tribal chief, the priest, the medicine man —are based on special talents. Plato described an ideal republic in which the citizens would be tested early in life and educated for positions in the state according to their capacities. As society became increasingly complex, and the idea of division of labor took hold, it became more and more necessary to appraise and classify individuals on the basis of ability, interest, and personality, for this was the only way to help them realize their potential and be of maximum service to the community. In addition, as the techniques of communication and transportation became more highly developed, nationalities, races, and social groups were brought into closer contact with each other, and this focused attention on the problem of group as well as individual differences.These historical developments constitute the general background for differential psychology, but more specific events shaped it into a scientific discipline. Darwin showed that species differ widely in the ways they adapt to the environment, and that some individuals have unique characteristics which enable them to compete and survive. Galton made some of the first studies of individual variations in skill and ability, measuring visual discrimination with the Galton bar and the range of hearing with the Galton whistle. Experimental psychologists turned their attention to quantitative investigations of sensory thresholds and motor abilities, and also helped to develop useful statistical concepts, such as average, deviation, and correlation. In about 1890, Cattell designed tests to measure differences in memory and reaction time, and in 1905 Binet created the first intelligence test. From that point onward, tests for practically every trait and ability were developed, and a wide range of human differences and similarities were investigated.These investigations have increased our appreciation of the uniqueness of the individual and the differences both within groups and between groups of all kinds. We now realize that many of the distinctions between the races, nationalities, and sexes have been too sharp, for there is considerable overlap between groups on practically any characteristic that can be named, and the variations within these groups are always greater than the differences between them. The exploration of differences has also led to continuous refinement in the crude classifications of 1. The artificial mother. Raised in isolation from its true mother, this monkey clings to a warm terry-cloth “mother surrogate,” even when it can obtain food only from a cold wire “mother.” 2. Is manipulation a basic drive? Like children, monkeys take things apart without any apparent reward other than the “monkeying” itself.Decisions, decisions, decisions. The monkey at the left has the responsibility of pressing a lever at intervals so that both may escape a mild electric shock. The lever at the right is not connected, and is soon ignored. The monkey at the left gets an ulcer—but not the one at the right.4. Can animals think? This duck has been trained to distinguish a triangle from other figures.

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