=Apperception a Law of Learning.=--In the study of the lesson process, Chapter III, attention was called to the fact that the interpretation which the mind places upon any presentation depends in large measure upon the mind's present content and interest. It is an essential characteristic of mind that it always attempts to give meaning to any new impression, no matter how strange that impression may be. This end is reached, however, only as the mind is able to apply to the presentation certain elements of former experience. Even in earliest infancy, impressions do not come to the organism as total strangers; for the organism is already endowed with instinctive tendencies to react in a definite manner to certain stimuli. As these reactions continue to repeat themselves, however, permanent modifications, as previously noted, are established in the nervous system, including both sensory and motor adjustments. Since, moreover, these sensory and motor adjustments give rise to ideas, they result in corresponding associations of mental imagery. As these neural and mental elements are thus organized into more and more complex masses, the recurrence of any element within an associated mass is able to reinstate the other elements. The result is that when a certain sensation is received, as, for instance, a sound stimulus, it reinstates sensory impressions and motor reactions together with their associated mental images, thus enabling the mind to assert that a dog is barking in the distance. In such a case, the present impression is evidently joined with, and interpreted through, what has already formed a part of our experience. What is true of this particular case is true of all cases. New presentations are always met and interpreted by some complex experiences with which they have something in common, otherwise the stimuli could not be attended to at all. This ability of the mind to interpret new presentations in terms of old knowledge on account of some connection they bear to that content, is known as _apperception_. In other words, apperception is the law of the mind to attend to such elements in a new presentation as possess some degree of _familiarity_ with the already assimilated experience, although there may be no distinct recognition of this familiarity.