Special fields of psychology

individual. When a score falls at the 50th percentile, for example, half of the group scored higher and half scored lower; a score at the 80th percentile indicates that 20 percent scored higher and 80 percent scored lower than the person being evaluated.

Standard scores are derived from a comparison of the individual raw score with the mean and standard deviation of the group scores. The mean, or arithmetic average, is determined by adding the scores and dividing by the total number of scores obtained. The standard deviation measures the variation of the scores around the mean. Standard scores are obtained by subtracting the mean from the raw score and then dividing by the standard deviation.

Tables of norms are included in test manuals to indicate the expected range of raw scores. Normative data are derived from studies in which the test has been administered to a large, representative group of people. The test manual should include a description of the sample of people used to establish norms, including age, sex, geographical location, and occupation. Norms based on a group of people whose major characteristics are markedly dissimilar from those of the person being tested do not provide a fair standard of comparison.

Validity. Interpretation of test scores ultimately involves predictions about a subject’s behavior in a specified situation. If a test is an accurate predictor, it is said to have good validity. Before validity can be demonstrated, a test must first yield consistent, reliable measurements. In addition to reliability, psychologists recognize three main types of validity.

A test has content validity if the sample of items in the test is representative of all the relevant items that might have been used. Words included in a spelling test, for example, should cover a wide range of difficulty.

Criterion-related validity refers to a test’s accuracy in specifying a future or concurrent outcome. For example, an art-aptitude test has predictive validity if high scores are achieved by those who later do well in art school. The concurrent validity of a new intelligence test may be demonstrated if its scores correlate closely with those of an already well-established test.

Construct validity is generally determined by investigating what psychological traits or qualities a test measures; that is, by demonstrating that certain patterns of human behavior account to some degree for performance on the test. A test measuring the trait “need for achievement,” for instance, might be shown to predict that high scorers work more independently, persist longer on problem-solving tasks, and do better in competitive situations than low scores.

Controversies. The major psychological testing controversies stem from two interrelated issues: technical shortcomings in test design and ethical problems in interpretation and application of results. Some technical weaknesses exist in all tests. Because of this, it is crucial that results be viewed as only one kind of information about any individual. Most criticisms of testing arise from the overvaluation of and inappropriate reliance on test results in making major life decisions. These criticisms have been particularly relevant in the case of intelligence testing. Psychologists generally agree that using tests to bar youngsters from educational opportunities, without careful consideration of past and present resources or motivation, is unethical. Because tests tend to draw on those skills associated with white, middle-class functioning, they may discriminate against disadvantaged and minority groups. As long as unequal learning opportunities exist, they will continue to be reflected in test results. In the U.S., therefore, some states have established laws that carefully define the use of tests in public schools and agencies. The American Psychological Association, meanwhile, continues to work actively to monitor and refine ethical standards and public policy recommendations regarding the use of psychological testing.

8. Development psychology

Developmental Psychology study of behavioral changes and continuity from infancy to old age. Much emphasis in psychology has been given to the child and to the deviant personality. Developmental psychology is particularly significant, then, in that it provides for formal study of children and adults at every stage of development through the life span.

Developmental psychology reflects the view that human development and behavior throughout the life span is a function of the interaction between biologically determined factors, such as height or temperament, and environmental influences, such as family, schooling, religion, and culture. Studies of these interactions focus on their consequences for people at different age levels. For example, developmental psychologists are interested in how children who were physically abused by their parents behave when they themselves become parents. Studies, although inconclusive, suggest that abused children often become abusive parents.

Other recent studies have focused on the relationship between the aging process and intellectual competence; contrary to the traditional notion that a person’s intellectual skills decline rapidly after the age of 55, research indicates that the decline is gradual. American studies of adulthood, building on the work of Erik Erikson, point to stable periods with a duration of 5 to 7 years, during which energy is expended on career, family, and social relationships, punctuated by “transitional” periods lasting 3 to 5 years, during which assessment and reappraisal of major life areas occurs. These transitional periods may be smooth or emotionally stormy; the “midlife crisis” is an example of such a transition. Whether such transitions are the same for men and women, and whether they are universal, is currently under study.

9. Social psychology

Social Psychology branch of psychology concerned with the scientific study of the behavior of individuals as influenced, directly or indirectly, by social stimuli. Social psychologists are interested in the thinking, emotions, desires, and judgments of individuals, as well as in their overt behavior. An individual’s inner states can be inferred only from some form of observable behavior. Research has also proved that people are affected by social stimuli whether or not they are actually in the presence of others and that virtually everything an individual does or experiences is influenced to some extent by present or previous social contacts.

Development of Theory. Social psychology is rooted in the earliest intellectual probes made by individuals into their relations with society. Many of the major problems of concern to contemporary social psychology were recognized as problems by social philosophers long before psychological questions were joined to scientific method. The questions posed by Aristotle, the Italian philosopher Niccol Machiavelli, the English philosopher Thomas Hobbes, and others throughout history are still asked, in altered form, in the work of present-day social psychologists.

The more recent history of social psychology begins with the publication in 1908 of two textbooks—each having the term social psychology in its title—that examine the impact of society on the development and behavior of individuals. One of these was written by the British psychologist William McDougall, and the other by the American sociologist Edward Alsworth Ross. McDougall framed a controversial theory of human instincts, conceived of as broad, purposive tendencies emerging from the evolutionary process. Ross, on the other hand, was concerned with the transmission of social behavior from person to person, such as the influence of one person’s emotions on another’s in a crowd, or the following of fads and fashions.

Another textbook on social psychology, published in 1924 by the American psychologist Floyd H. Allport, had an important influence on the development of social psychology as a specialization of general psychology. Allport extended the principles of associative learning to account for a wide range of social behavior. He thus avoided reference either to such mysterious social forces as were proposed by Ross or to the elaborate instinctive dispositions used by McDougall and his followers to account for social behavior. Through the remainder of the decade, the literature of social psychology continued to be devoted to similar discussions and controversies about points of view, and little empirical work, that is, work relying on experience or observation, of theoretical or practical significance was done.

Early Experimentation. In the 1930s empirical research was first undertaken on such matters as animal social behavior, group problem-solving, attitudes and persuasion, national and ethnic stereotypes, rumor transmission, and leadership. The German-American psychologist Kurt Lewin emphasized the necessity of doing theoretical analysis before conducting research on a problem, the purpose of the research being to clarify explanatory mechanisms hypothesized to underlie the behavior being studied. The theory proposes an explanation of certain behavior and allows the investigator to predict the specific conditions under which the behavior will or will not occur. The investigator then designs experiments in which the appropriate conditions are methodically varied and the occurrence of the behavior can be observed and measured. The results allow modifications and extensions of the theory to be made.

In 1939 Lewin together with two of his doctoral students published the results of an experiment of significant historical importance. The investigators had arranged to have the same adults play different