Page:Popular Science Monthly Volume 42.djvu/45

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O any one thoroughly impressed with the intimate relations of mind and body, it seems natural enough that the gradual development and perfection of the one should carry with it analogous stages in the growth of the other; but even the most profound student must at times give wondering expression to the marvelous extent, the endless variety, and the unexpected precision of the interrelations of the physical and the psychological. An extensive survey of the phenomena to be studied, and a discerning and comprehensive use of the comparative method in studying them, are as necessary and as promising in the mental as they have proved to be in the physical sciences. We must overcome the tendency to study too exclusively our own adult, civilized, conscious selves; to view the landscape by observing its reflection in a mirror, and thus seeing everywhere our own image. With full appreciation of the supreme interest we must always have in our own mental powers, it may be maintained that in proportion to our knowledge of the earlier, simpler, and lowlier manifestations of intelligence, will be our ability to appreciate and utilize the best and worthiest faculties in ourselves.

Comparative Psychology finds its origin and its material in the variety of animal life, in the series of changes of which an individual life consists, and in the evolution of more complex forms of life from one generation to another. The first of these—Animal Psychology—endeavors to arrange in orderly sequence the various forms of mentality from protozoon to man, to discover in what this advance consists, to establish orderly relations between mental powers and the nervous system, and the like. The study of the stages, and especially the earlier stages, of the growth of the human mind—Child Psychology—has only recently been pursued in a scientific spirit, so that systematic records of the essential and important points of child-growth are lamentably rare. But even this limited research has brought to light an interesting body of facts, and holds out the promise of more valuable results as the fruits of more extended investigation. The side of anthropology that deals with the stages of man's mental progress from rudest savagery to the highest civilization; tracing the variety and onward movements of customs, habits of thought,