II.

History

The science of psychology developed from many diverse sources, but its origins as a science may be traced to ancient Greece.

A.

Philosophical Beginnings

Plato and Aristotle, as well as other Greek philosophers, took up some of the basic questions of psychology that are still under study: those to do with whether people are born with certain skills, abilities, and personality, or whether these develop as a result of experience. They ask how people come to know the world and how we can account for the manifest differences between people.

Such questions were debated for many centuries, but the roots of modern psychological theory are found in the 17th century in the works of the French philosopher René Descartes and the British philosophers Thomas Hobbes and John Locke. Descartes argued that the bodies of people are like clockwork machines, but that their minds (or souls) are separate and unique. He maintained that minds have certain inborn, or innate, ideas and that these ideas are crucial in organizing people’s experiencing of the world. Hobbes and Locke, on the other hand, stressed the role of experience as the source of human knowledge. Locke believed that all information about the physical world comes through the senses and that all correct ideas can be traced to the sensory information on which they are based.

Most modern psychology developed along the lines of Locke’s view. Some European psychologists who studied perception, however, held on to Descartes’s idea that some mental organization is innate, and the concept still plays a role in theories of perception and cognition (thinking and reasoning). It is also seen in Noam Chomsky‘s theory of language, and in Carl Gustav Jung‘s more speculative theory of personality. More generally, current research is revealing in detail how much “nature” contributes to the causes of behaviour, as compared to “nurture”.

B.

Scientific Developments

Against this philosophical background, the field that contributed most to the development of scientific psychology was physiology—the study of the functions of the various organ systems of the body. The German physiologist Johannes Müller tried to relate sensory experience both to events in the nervous system and to events in the organism’s physical environment. The first true exponents of experimental psychology were the German physicist Gustav Theodor Fechner and the German physiologist Wilhelm Wundt. Fechner developed experimental methods for measuring sensations in terms of the physical magnitude of the stimuli producing them. Wundt, who in Leipzig, Germany, in 1879 founded the first laboratory of experimental psychology, trained students from around the world in the new science.

This experimental tradition rested on the assumption that the basic mechanisms and units of behaviour could be identified, in a way analogous to the physical sciences. Human beings, however, are essentially individuals, differing from each other in important ways. The scientific measurement of individual differences (psychometrics) can be said to take as its starting point the work of Francis Galton, in particular his book Hereditary Genius (1869). He also showed how, in principle, the origins of these differences could be traced to the relative effects of heredity and environment.

Medical practitioners who became concerned with mental illness also contributed to the development of modern psychological theories. Thus, the systematic classification of mental disorders developed by the German psychiatric pioneer Emil Kraepelin, which was the original method of classification, is still in use. Far better known, however, is the work of Sigmund Freud, who devised the system of investigation and treatment known as psychoanalysis. Freud called attention to instinctual drives and unconscious motivational processes that determine people’s behaviour. His stress on the dynamics of behaviour—that is, what makes people do things—and on the importance of early childhood, exerted a strong influence on the course of modern psychology, although most of his detailed theories have not been well supported by later research.

C.

20th-Century Psychology

In both the United Kingdom and the United States, psychology was influenced greatly by practical considerations, with practitioners applying psychological methods in school and business settings. In America, in particular, experiment and theory came to be dominated, until about 1960, by the behaviourist movement led originally by John B. Watson. This paid little attention to mental processes, focusing instead on observable behaviour.

A much more sophisticated version of the experimental analysis of behaviour was developed by Burrhus F. Skinner. This was overtaken, however, by the growth of a new cognitive psychology movement, which restored mental processes to their central role, drawing in particular on work in artificial intelligence (AI) and the computer simulation of behaviour.

Even more recently, a great deal of research has appeared in, on the one hand, cultural and developmental factors in behaviour, and on the other, behavioural genetics—that is, the inherited factors. At the same time applications of psychology have proliferated.

D.

Psychological Approach and Methods

Popularly, a psychological approach is sometimes equated with a “soft” approach, or thought to be concerned merely with thoughts and feelings. In fact, psychologists seek the most effective means of dealing with human problems, whatever they may be, based on hard facts and what has been proved to work. Similarly, theories must be tested continually against evidence.

Obtaining such evidence is often not easy. People are extremely diverse and changeable, and many methods of investigation are ethically or practically impossible. It is also the case that human behaviour is very rarely a simple result of one factor; it almost always has multiple causes, a situation often ignored by those who urge one simple cure for crime or educational failure, for example. This complexity means that sophisticated statistical methods have to be used to tease out the effects of multiple variables.

Where possible, experiment is the preferred method of collecting data; some factors are held constant, and others varied. Sometimes a “natural” experiment can be used, as in twin studies: identical twins effectively share the same heredity, whereas non-identical ones are no more alike than any pair of siblings. Sometimes it is simply a matter of establishing the views or attitudes of a specific group of people, as in consumer research, perhaps using interviews, questionnaires, or group discussions. Even then there will probably be sub-groups, such as men and women, or older and younger people, that need to be analysed separately. Other techniques often used include systematic observation of natural behaviour, such as children’s play, and introspection, that is, asking a person to say what is going through his or her mind, for example, when solving a problem. Physiological psychology uses physical recording techniques, for example of the electrical activity of the brain, hormone levels, and heart rate.

E.

Tests and Measurements

Tests, especially intelligence tests, are perhaps the psychological technique that is most often met with in everyday life. “Tests” is in fact an unfortunate term, as it implies success or failure. Most psychological measures are simply intended to give an accurate picture of an individual or group, compared to others, on characteristics that are likely to be relatively permanent. These characteristics are usually either abilities (such as general intelligence, or specialized abilities for, for example, mathematics, music, or sport) or personality traits, such as introversion-extroversion, that is, how inward-looking or outgoing a person may be.

Methods of measuring these, like all scientific measurements, must be both valid and reliable. Reliability means that the same score will result under the same conditions, just as a thermometer must always give the same reading when the temperature is identical. Validity means that it is known what is being measured; a thermometer must respond to temperature, but not to, for instance, air pressure.

Psychological measures have an added difficulty in that norms have to be established based on some sample of the population; it is impossible to measure all the human race. This has led to controversy over intelligence tests in particular, when it appears that some groups perform, on average, better or worse than others. The reasons for this are still not well understood. There is also argument over what “intelligence” means; but technically, it refers simply to the fact that performances on a range of cognitive (roughly, “thinking”) tasks tend to correlate.