Introduction to Psychophysiology
In the first edition of this book, I wrote that "the field of psychophysiology is concerned with the measurement of physiological responses as they relate to behavior." The word behavior is used now, as then, in the broadest sense to include such diverse activities as sleep, problem solving, reactions to stress, learning, memory, information processing, perception, or--in short--any of the activities that psychologists are inclined to study. This characterization of the field requires some clarification. You, the reader, may ask how psychophysiology differs from the discipline traditionally known as physiological psychology; the answer is that it is mainly in the approach and subject matter of these areas, because the goal of understanding the physiology of behavior is the same.
Distinctions have been made between psychophysiology and physiological psychology in terms of how dependent and independent variables are used ( Lykken, 1984; Stern, 1964). The dependent variables refer to what is actually being measured in a research project, and the independent variable is the aspect being manipulated. Stern and Lykken said that in psychophysiology, the dependent variables are physiological (e.g., heart rate) and the independent variables are psychological (e.g., problem solving). However, in physiological psychology the dependent variables are mainly psychological (learning, or perceptual accuracy, as examples), whereas independent variables are physiological (e.g., brain stimulation or removal of brain tissue). This distinction in terms of dependent and independent variables is useful but not entirely satisfactory to Furedy ( 1983), who argued that this approach does not cover the example of a physiological psychologist who records and studies changes in a single neuron while psychological stimuli are manipulated. According to Furedy's definition: "Psychophysiology is the study of psychological processes in the intact organism as a whole by means of unobtrusively measured physiological processes" (p. 13). He emphasized that a measurement made unobtrusively, as with surface electrodes, results in a more accurate picture of the behaving organism. Mangina ( 1983) objected to Furedy's use of the term "intact organism" because this would exclude the study of brain damaged, mentally retarded, or drug-influenced persons, and patients suffering from various psychophysiological disorders. Mangina defined psychophysiology as "the science which studies the physiology of psychic functions through the brain-body-interrelationships of the living organism in conjunction with the environment" (p. 22).
At this point, I propose a definition that attempts to integrate those previously offered: Psychophysiology is the study of relations between psychological manipulations and resulting physiological responses, measured in the living organism, to promote understanding of the relation between mental and bodily processes. I believe this definition can provide a useful starting point.