INDIVIDUAL PSYCHOLOGY. This term is applied to that branch of psychology which deals with the mental variations of in dividuals from one another. It is thus contra distinguished from general psychology, which undertakes to determine the facts and laws of conscious processes as a whole and without special reference to their peculiar manifesta tions in any particular persons or group of per sons. The field of individual psychology may be regarded as a part of the larger field of varia tional or differential psychology in which are to be included studies upon special races and upon social groups of various sorts. Such studies are carried on with special reference to detect ing and describing the characteristic mental traits of such groups, but often with little em phasis on typical variations from other similar groups. Obviously the range of problems in individual psychology must be as broad as mind itself, for persons may vary in regard to any mental characteristic. It will only be prac ticable to mention a few of the problems thus far investigated, e.g., mental type, tempera ment and genius, the psychology of special mental defect, the psychology of the criminal, the psychology of sex, and that of professions or classes with their peculiar variations of men tal constitution.
To exhibit more concretely the kind of material with which individual psychology works we may comment briefly on the first three of these topics. The determination of mental type is a problem of individual psychol ogy in the narrow sense of the term in so far as it has to do with the ascertaining of the characteristic features of the mind of any par ticular person. In so far as it bears on the problem of discovering what actually are the typical groupings of such characteristics among people in general, it obviously belongs to the broader field of variational psychology.
1. Minds may differ from each other as re gards the delicacy or sensitiveness with which they respond to stimulations of the sense organs. One may be more sensitive than an other to slight variations in temperature, in color, in tone, etc. As a matter of fact, among normal persons such differences of • sensitivity are relatively slight when the conditions of training and discipline are similar. As a gen eral rule the higher mental functions show more variation than the lower one such as sensitivity. Minds may differ as regards the special form of sense material toward which they manifest a predilection, e.g., the musically minded person not only finds sounds of greater emotional interest than the unmusical person, but he also has a better memory for auditory experiences and his conscious processes in their entirety are likely to be much more influenced by auditory factors. A further development of
such mental preference for one or another kind of sense material is found in the fact that cer tain individuals carry on most of their thought processes in terms of visual images, whereas others employ auditory images, and still others motor images. Probably the normal condition is represented by an admixture of various forms with some particular group dominating slightly over the others. Again, in memory we meet striking differences in addition to those of the imagery type already mentioned. For example, certain persons learn very rapidly and also forget rapidly. Others learn with diffi culty but retain well that which they have learned. Occasionally we find persons who combine ability to learn qqickly with capacity to retain permanently. It seems certain from psychological investigations that individuals supposed to possess particularly good memories are generally proficient only in certain direc tions. A universally efficient memory is rarely, if ever, found. People differ also very mark edly as regards their ability to concentrate their attention. Some persons can concentrate very intensely for a short time but must then rest. Others are able to focalize for more extended periods, and still others find it all but impossible ever to secure any intense concentration. Variations of a striking kind are also disclosed in the formation of judgments. Certain per sons judge almost entirely in accord with the objective facts presented to their notice. Others are influenced in various degrees by subjective influences and show themselves peculiarly sus ceptible to suggestion. It is a matter of com mon observation that persons vary radically as regards temperament and feeling. One of the most practically important variations is represented by the difference in the rate at which the conscious processes proceed. Just as certain persons naturally walk and talk more rapidly than others, so do the mental processes vary as regards the speed with which they occur. Psychologists have demonstrated a rather characteristic daily variation as regards both rate and efficiency of mental activity. Many persons work best at night. Others are morning workers and still others afternoon workers.