These illustrations are typical of our life. Every moment we have perceptions. These perceptions arouse ideas of our past life and experience. One of these ideas evokes another, and so an endless chain of images passes along. The older we become, the richer is our ideational life. While we are children, the perceptions constitute the larger part of our mental life, but as we become older, larger and larger becomes the part played by our memory images or ideas. A child is not content to sit down and reflect, giving himself up to the flow of ideas that come up from his past experience, but a mature person can spend hours in recalling past experience. This means that the older we grow, the more we live in the past, the less we are bound down by the present, and when we are old, instead of perceptions being the main part of mental life, they but give the initial push to our thoughts which go on in an endless chain as long as we live.
The Physiological Basis of Memory. It will be remembered that the basis of perception is the agitation of the brain caused by the stimulation of a sense organ by an external thing or force. If there is no stimulation of a sense organ, there is no sensation, no perception. Now, just as the basis of sensation and perception is brain activity, so it is also the basis of ideas. In sensation, the brain activity is set up from without. In memory, when we have ideas, the brain activity is set up from within and is a fainter revival of the activity originally caused by the stimulation of the sense organ. Our ideas are just as truly conditioned or caused by brain activity as are our sensations.
Memory presents many problems, and psychologists have been trying for many years to solve them. We shall now see what they have discovered and what is the practical significance of the facts.
Relation of Memory to Age and Sex. It is a common notion that memory is best when we are young, but such is not the case. Numerous experiments have shown that all aspects of memory improve with age. Some aspects of memory improve more than others, and they improve at different times and rates; but all aspects do improve. From the beginning of school age to about fourteen years of age the improvement of most aspects of memory is rapid.
If we pronounce a number of digits to a child of six, it can reproduce but few of them, a child of eight or ten can reproduce more, a child of twelve can reproduce still more, and an adult still more. If we read a sentence to children of different ages, we find that the older children can reproduce a longer sentence. If we read a short story to children of different ages, and then require them to reproduce the story in their own words, the older children reproduce more of the story than do the young children.[5]
[5] See age and sex graphs, pp. [184], [188], [189].
Girls excel boys in practically all the aspects of memory.
In rote memory, that is, memory for lists of unrelated words, there is not much difference; but the girls are somewhat better. However, in the ability to remember the ideas of a story, girls excel boys at every age. This superiority of girls over boys is not merely a matter of memory. A girl is superior to a boy of the same age in nearly every way. This is merely a fact of development. A girl develops faster than a boy, she reaches maturity more quickly, in mind as well as in body. Although a girl is lighter than a boy at birth, on the average she gains in weight faster and is heavier at twelve than a boy of the same age. She also gains faster in height, and for a few years in early adolescence is taller than a boy of the same age. Of course, boys catch up and finally become much taller and heavier than girls. Similarly, a girl’s mind develops faster than the mind of a boy, as shown in memory and other mental functions.
The Improvement of Memory by Practice. All aspects of memory can be improved by practice, some aspects much, other aspects little. The memory span for digits, or letters, or words, or for objects cannot be much improved, but memory for ideas that are related, as the ideas of a story, can be considerably improved. In extensive experiments conducted in the author’s laboratory, it was found that a person who at first required an hour to memorize the ideas in a certain amount of material, could, after a few months’ practice, memorize the same amount in fifteen minutes. And in the latter case the ideas would be better remembered than they were at the beginning of the experiment. Not only could a given number of ideas be learned in less time, but they would be better retained when learned in the shorter time. If a person comes to us for advice as to how to improve his memory, what should we tell him? In order to answer the question, we must consider the factors of a good memory.
Factors of a Good Memory. (1) The first requirement is to get a good impression in the beginning. Memory is revived experience. The more vivid and intense the first experience, the more sure will be the later recall. So if we wish to remember an experience, we must experience it in the first place under the most favorable conditions. The thing must be seen clearly, it must be understood, it must be in the focus of consciousness.