Memory and Habit. The discussion up to this point should have made it clear to the reader that memory is much the same thing as habit. Memory considered as retention depends upon the permanence of the impression on the brain; but in its associative aspects depends on connections between brain centers, as is the case with habit. The association of ideas, which is the basis of their recall, is purely a matter of habit formation.
When I think of George Washington, I also think of the Revolution, of the government, of the presidency, of John Adams, Thomas Jefferson, etc., because of the connections which these ideas have had in my mind many times before. There is a basis in the brain structure for these connections. There is nothing in any idea that connects it with another idea. Ideas become connected because of the way in which we experience them, and the reason one idea calls up another idea is because the brain process that is the cause of one idea brings about another brain process that is the cause of a second idea. The whole thing is merely a matter of the way the brain activities become organized. Therefore the various laws of habit-formation have application to memory in so far as memory is a matter of the association of ideas, based on brain processes.
One often has the experience of trying to recall a name or a fact and finds that he cannot. Presently the name or fact may come, or it may not come till the next day or the next week. What is the cause of this peculiar phenomenon? The explanation is to be found in the nervous system. When one tries to recall the name and it will not come to mind, there is some temporary block or hindrance in the nerve-path that leads from one center to the other and one cannot think of the name till the obstruction is removed. We go on thinking about other things, and in the meantime the activities going on in the brain remove the obstruction; so when the matter comes up again, the nerve current shoots through, and behold, the name comes to mind.
Figure IV—Associative Connections
The diagram represents schematically the neural basis of the association of ideas.
Now the only preventive of such an occurrence is to be found in the law of habit, for the block ordinarily occurs in case of paths or bonds not well established. We must think together the things we wish to have associated. Repetition is the key to the situation, repetition which is the significant thing in habit-formation, repetition which is the only way of coupling two things which we wish to have associated together.
Of course, there is no absolute coupling of two ideas. One sometimes forgets his own name. When we are tired or ill, things which were the most closely associated may not hang together. But those ideas hold together in the firmest way that have been experienced together most often in a state of attention. The diagram on page [147] illustrates schematically the neural connections and cross-connections which are the bases of the association of ideas, the circles A, B, C, D, E, and F represent brain processes which give rise to ideas, and the lines represent connecting paths. Note that there are both direct and indirect connections.
Summary. Sensation and perception give us our first experience with things; memory is revived experience. It enables us to live our experience over again and is therefore one of the most important human traits. The physiological basis of memory is in the brain and nervous system. Memory improves with practice and up to a certain point with the age of the person. It is better in girls than in boys. Good memory depends on vivid experience in the first place and on organization and repetition afterward. The person who learns quickly usually retains well also. Memory training is specific. The extension of the learning process over a long time is favorable to memory. Memory ideas are the basis of thinking and reasoning.