The vertical dimensions of mind

In spite of the traditional bias in psychology toward cross-sectional analysis, interest is growing in the opposite type--long-sectional analysis, whose two major dimensions are maturation-degeneration and learning-forgetting. Learning pervades every psychological phenomenon--perception, ideation, emotion, motivation, volition--for each is merely a brief cross-sectional glimpse of the unbroken flow of change involved in the learning-forgetting continuum. The implications of this for experimental attack upon and systematization of the problems of psychology are brought out. This viewpoint not only emphasizes the necessity for a more adequate attack on the special problems of learning itself, but calls for a re-examination of every psychological category in the light of the longitudinal approach.