A biological theory about the development of the embryo which stresses the influence of the environment. The interaction of embryo and environment produces new properties that were not present in the fertilised egg, or ZYGOTE. In certain psychological theories, especially those of ERIK ERIKSON, epigenesis refers to a sequence of developmental stages that must be followed to attain psychological maturity.

The tendency to regard the group one identifies with, especially one’s ethnic group, as superior to any other. Like EGOCENTRICITY in individuals, it involves the inability to step outside the perceptual framework of one’s own group and see life from the viewpoint of a different group.

is a methodological approach rather than a subject and encompasses varied fields within psychology. Experimental psychologists have traditionally conducted research, published articles, and taught classes on neuroscience, developmental psychology, sensation, perception, attention, consciousness, learning, memory, thinking, and language. Recently, however, the experimental approach has extended to motivation, emotion, and social psychology. Experimental psychologists conduct research with the help of experimental methods. The concern of experimental psychology is discovering the processes underlying behavior and cognition, as well as PHENOMENA.

The branch of PHILOSOPHY that deals with the search for true knowledge: the origins, nature, limits and verifiability of what is known.

The effects on an EXPERIMENT of the CONSCIOUS or UNCONSCIOUS attempts by the experimenter to influence the outcome in the direction predicted. This is an important and pervasive problem, as the outcome of virtually every published experiment is in the predicted direction. The ramifications of this PHENOMENON are much wider than the experimental situation.

See also DEMAND CHARACTERISTICS, DOUBLE-BLIND TECHNIQUE, INTERVIEWER BIAS, ROSENTHAL EFFECT and SELF-FULFILLING PROPHECY.

A drug, like LSD or mescaline, that induces HALLUCINATION.

Named after the German physicist and psychologist Gustav Fechner. Large increases in the intensity of a stimulus produce smaller, proportional increases in the intensity perceived. It is expressed mathematically as S=k log R, where S is the intensity experienced, R is the actual physical intensity and k is a constant. This is one of the first attempts at a mathematical statement of a psychological PHENOMENON. It grew out of the studies in PSYCHOPHYSICS with which PSYCHOLOGY became an experimental science in the 1870s.

The BELL-SHAPED CURVE of a NORMAL DISTRIBUTION, named after Carl Gauss, a nineteenth-century German mathematician.

Technically, the investigation of the way in which the INDEPENDENT VARIABLE in an EXPERIMENT affects the DEPENDENT VARIABLE, but the term is used more generally for the whole procedure of an experiment, from the selection of subjects to the statistical analysis of the results.

The pleasantness or unpleasantness of the sensation one experiences from the stimulus of a given person, object or situation.