MNEMONIC DEVICES.--Many ingenious devices have been invented to assist the memory. No doubt each one of you has some way of your own of remembering certain things committed to you, or some much-needed fact which has a tendency to elude you. You may not tie the traditional string around your finger or place your watch in the wrong pocket; but if not, you have invented some method which suits your convenience better. While many books have been written, and many lectures given exploiting mnemonic systems, they are, however, all founded upon the same general principle: namely, that of _association of ideas_ in the mind. They all make use of the same basis for memory that any of us use every time we remember anything, from the commonest event which occurred last hour to the most abstruse bit of philosophy which we may have in our minds. They all tie the fact to be remembered to some other fact which is sure of recall, and then trust the old fact to bring the new along with it when it again comes into the mind. Artificial devices may be permissible in remembering the class of facts which have no logical associates in which we can relate them; but even then I cannot help feeling that if we should use the same care and ingenuity in carefully recording the seemingly unrelated facts that we do in working out the device and making the association in it, we should discover hidden relations for most of the facts we wish to remember, and we should be able to insure their recall as certainly and in a better way than through the device. Then, also, we should not be in danger of handing over to the device various facts for which we should discover relations, thus placing them in the logical body of our usable knowledge where they belong. 8. PROBLEMS IN OBSERVATION AND INTROSPECTION 1. Carefully consider your own powers of memory and see whether you can decide which of the four types of brain you have. Apply similar tests to your classmates or a group of school children whom you have a chance to observe. Be sure to take into account the effects of past training or habits of memory. 2. Watch in your own memorizing and also that of school children for failures in recall caused by lack of proper associations. Why is it particularly hard to commit what one does not understand? 3. Observe a class in a recitation or an examination and seek to discover whether any defects of memory revealed are to be explained by lack of (1) repetition, (2) recency, (3) vividness in learning. 4. Make a study of your own class and also of a group of children in school to discover their methods of memorizing. Have in mind the rules for memorizing given in section 5 of this chapter.