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LESSON XXV.

MEMORY.

Elements of Memory. We can conceive of a mind with no capacity except the power to experience sensations a mind limited to the present - a mind whose experiences leave no trace upon it. Such a mind would be destitute of the power of retention. We can conceive of a mind like our own in that every sensation, every experience leaves "the mind different, as every physical change leaves the body different," but unlike ours in that an experience once gone never returns. As every minute in that stately and solemn procession that we call the March of the Years goes by never to return, so we can conceive that the shadow of those experiences that we are conscious of from moment to moment, in spite of the fact that each of them left the mind different, might never fall across our conscious life. Such a mind would be without the power of reproduction. We can conceive of a mind, also, with laws of association like our own a mind constantly conscious of images of some of its past experiences, but without the faintest notion that they were images—a mind with the power to make pictures or copies of past events, but without the power to refer them to their original. Such a mind would be destitute of the power of re-cogni tion-re-knowing. Or we can conceive of a mind with

RETENTION.

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the power to reproduce and re-know its past experiences, but without the power to locate them a mind to which "yesterday," "last week," "last month," "last year," would mean the same thing the past, a mind all of whose recollections were like those we have sometimes been conscious of when we have seen a face that we were sure we had seen before, but with no idea of where or when. Such a mind would be without the power of localization.1

These four powers, then-retention, reproduction, recognition, and localization-constitute the power that we call memory. You would not, indeed, say that you do not remember a thing when you are not thinking about it. But you would say that a mind that did not possess all four of these powers can not remember as we can, and that one without the last two can not remember at all. A complete explanation of memory, then, would require a complete explanation of these four powers.

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Retention. In thinking about retention, we must be on our guard against being led into mistakes by the literal meaning of the word. The act of retaining seems to imply a place where things are retained, and so we sometimes permit ourselves to think of memory as a great storehouse, where all the lumber of our past experience is accumulated. This was the opinion of Herbart. Says the Herbartian, Lindner: "That concepts are not destroyed by passing out of consciousness is proved by the fact of reproduction." And Leibniz: "No idea leaves the mind, but each idea becomes invisible for a time or permanently. To remember is to have new consciousness of what has not ceased

1 See Baldwin's Psychology, p. 151.

to exist in the soul."

But when we begin to think seribelieve that the "storehouse" of

ously, it is hard to memory is more than a metaphor. I had the toothache yesterday; to-day I recall the fact. I have an image of it. But the image or idea of the toothache is not the original fact. The toothache was intensely painful; the image of it is not at all so. If you ask where the image was from the time it dropped out of consciousness until the time we thought of it to-day, the proper answer is, as Baldwin says, Nowhere. When I had the toothache, I was conscious of a sensation. When I ceased to have it, the sensation ceased. When the idea of it is recalled to my mind, I remember it. Between the disappearance of the sensation and the rise of the image my mind was inactive with reference to it; there was neither sensation nor image of it in existence. So far as consciousness is concerned, then, retention does not denote an act, but states a fact the fact that experiences of the past leave the mind different, since it often happens that we can recall them.

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Retention a Physical Fact. The probability is that retention is, in part at least, a purely physical fact. The facts already cited in an earlier chapter of impairment of memory in consequence of an injury to the brain indicate this. Ribot states the argument very forcibly : "If, with closed eyes, we keep for a length of time an image of very lively colors before the imagination, and then opening the eyes suddenly, we fix them upon a white surface, we see thereon for an instant the image contemplated in imagination, but in the complementary color. This fact, as is observed by Wundt, from whom we borrow it, proves that the nerve action is the same in the two

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LAWS OF ASSOCIATION.

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cases in the sense perception and in the memory.' Professor Ladd also puts the case clearly: "That the mental phenomena which lead us to speak of the retentive power of memory have a physical basis, there can be no doubt. . Every sensory impulse must produce changes both in the end organs and the central organs; and although these changes vanish, so far as their effect in the corresponding phenomena of conscious mind is concerned, they nevertheless can not fail to leave the organs in different condition from that in which they were found." Fouillée makes a concise and graphic statement of some of the facts that support this opinion: "It is evident that there is in memory something automatic, capable of functioning alone; even the diseases and illusions to which it is subject prove that there is something delicate and fragile. in this marvel of natural mechanism. If a scholar, after having received a violent blow on the head, forgets all his knowledge of Greek without forgetting anything else, and if afterwards, as the result of a second blow, he suddenly regains his lost Greek, it is difficult to see in memory an act entirely spiritual.”

Reproduction and Laws of Association.

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The laws. in accordance with which ideas and images of our past experiences arise in our minds have already been considered. They are, as we know, the laws of association. We say that any thought, idea, or experience tends to recall similar thoughts, ideas, or experiences, and all other thoughts or experiences that were in the mind at the same time.

A consideration of this law will enable us to see how it 1 Ladd's Physiological Psychology, p. 548

happens that we are sometimes conscious of re-knowing things without being able to recall the place where, or the time when, the thing was originally known, or any of the circumstances connected with it. It is because the thing recalls the past experience simply by the law of association by similarity. Usually, as we know, along with the similar idea are recalled other ideas or thoughts that were in the mind at the same time; and it is these other thoughts or ideas that enable us to localize our recollections. You saw a stranger yesterday in the post-office.

To-day you see

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him again, and as soon as you see him you are conscious of that feeling of recognition—you know that you have seen him before. How do you know it? Because of the likeness between your percept of him and the image that arises in the mind. But suppose the image comes entirely unattended suppose it comes without of the other ideas that were in the mind at the same time then you will have the feeling that you are re-knowing the person, but where or when you originally knew him you will be utterly unable to tell. You will not know where, for by supposition the image of the post-office does not come into your mind with the image of the person you saw there. You will not know when, for none of the images or thoughts that fix the time come with the image no thought of yesterday, no thought of what you were or had been doing. As we can not locate the place of a thing except in relation to other places - London in relation to England, England to Europe, Europe to the earth, the earth to the solar system, the solar system to the universe, the universe to what? so we can not locate the time of an event except with reference to the time of other events, succeeding, preceding, or contemporaneous. (What does

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