The purpose of this essay is to identify the research area of psychophysiology by abstracting the goals and methods from reports which this author believes are properly called psychophysiological. The general goal of psychophysiology is to describe the mechanisms which translate between psychological and physiological systems of the organism. Specific goals are to identify and describe the physiological processes directly relevant to such psychological constructs as drive, motivation, attitude, emotion, and their modification by learning. Findings include the description by physiological patterns of several emotions, sleep, dreaming, hypnosis, psychiatric and psychosomatic conditions. Principles conceived are individual, stimulus, emotion and attitude specificities and the law of initial values. The progressive theme of psychophysiological method has been to extend measurement to more covert behavior with decreasing interference with the organism. Methods and special problem areas are reviewed under the categories of (a) the stimulus situation, (b) observation (sensors, recorders, signal transformation), and (c) analysis, synthesis, and interpretation. The major unsolved technical problem is the automatic detection of artifact. The chief theoretical problem is to "break the code" by which the organism translates between experience and physiology. The psychophysiological method is seen as having useful application in classification and training for motivational abilities and stress tolerance. [ABSTRACT FROM AUTHOR]