MEMORY AND ITS DISORDERS. Locke has defined memory as power tie mind has to revive perceptions which it once had, with the additional perception that it has had them before.° Ribot distinguishes three functions of memory: (1) the preservation r• certain states, (2) their reproduction and (3 their recognition. In view of the fact that collection of gray matter in the cerebro-spini axis below the cortex is capable of storing im pressions and that probably all parts of the sensory nervous system are concerned in mkt' action and in memory, it will be necessary t: speak not merely of memory but of memories in the sense of reproductions of like sense quality with the original impressions. Modax. psychology accepts the concept of unconscicm memory, which would imply that all impres sions upon all sense organs are permanenti-, retained in the organism. In this case the tion is not so much how we remember as wh-, we forget. An. answer to this question has been found by the present day analytical inT chology of the unconscious. Up to the use of the acceptance of these views the deter minants of memory were considered to be fre quency of repetition of the stimulus, or 1:1, intensity, or its interest or a combination these factors. From a purely mechanical of view memory is interpretable as a result c: a biochemical phenomenon. The sensory cells, being acted on by certain stimuli, wheiht: of touch, taste, hearing or undergo cer tain molecular changes. Repetition of similar impulses induces similar reactions and a habit ual response in the affected cells results. A line of least resistance is established and it these habitual responses the germ of the ides of memory is to be found.
From this point of view the nerve-cells re tain something as a result of a previous ex perience, and the repetition of the stimuli' finds the cells in a receptive state. repetition of the stimuli constitutes a memcr,. and in this sense the training of a cerar mechanism has bound up in it this mechanics theory of memory. Thus a muscular efkr. as in tennis, or skating, or piano-playing, be comes by repetition remembered in automatic action, frequently without consciousness. It i
the usual rule that many muscular acts in their acquisition have called for memories soon become automatic, and the effr no longer rises into consciousness, perhaps be cause of its diminished intensity. A stenib point of view may be held for sions, for taste, for touch, for sight, in earh individual case a different series of nerve-ceP and nerve-fibres being involved. Thus rhe memory for a poem may mean a habit-respong to a series of sight or sound impressions, or a: the muscular memories of the speech medur ism that has learned to repeat the phrases. The actor who automatically says his lines, ohm not conscious of what he is saying, the pianie who mechanically plays, or the golfer who un consciously drives true, all show the same of memory adaptations, involving different nervous chains.
There are thus not only a visual manor., but an auditory memory, or memory for sottn&. a gustatory memory for tastes, an olfactory for smells, and special memories for the other special classes of sensation. Older psychology was concerned with the question as to the fidelity and longevity of these special memories or types of memory, as related to each other, and with the discovery of laws according to which they . might be revived. (See Mitt toadies). But with the introduction of the unconscious as a dynamic factor, the recalling of a previous experience is explained on a new principle. Memories are thus seen in the form of ideas to be • reproduced into consciousness by • virtue of forces which are mainly unconscious, and over winch consciousness has only an indirect control, and the study of memory as such re tires to an importance secondary to the study of the causes why some things 'tend td be rtmem berefl and others tend to be forgotten. This trend or tendency on one hand to be for gotten or on the other to be remembered is now known to be determined by the unconscious wish, a force which is termed the libido and which is the prime mover, although uniformly unrecognized, of all the activities of the ego, both conscious and unconscious.