HOW WE REMEMBER.--Now, if we are to have a once-known fact repeated in consciousness, or in other words _remembered_, what we must do on the physiological side is to provide for a repetition of the neural activity which was at first responsible for the fact's appearing in consciousness. The mental accompaniment of the repeated activity _is the memory_. Thus, as _memory is the approximate repetition of once-experienced mental states or facts, together with the recognition of their belonging to our past, so it is accomplished by an approximate repetition of the once-performed neural process in the cortex which originally accompanied these states or facts_.
The part played by the brain in memory makes it easy to understand why we find it so impossible to memorize or to recall when the brain is fatigued from long hours of work or lack of sleep. It also explains the derangement in memory that often comes from an injury to the brain, or from the toxins of alcohol, drugs or disease.
DEPENDENCE OF MEMORY ON BRAIN QUALITY.--Differences in memory ability, while depending in part on the training memory receives, rest ultimately on the memory-quality of the brain. James tells us that four distinct types of brains may be distinguished, and he describes them as follows:
(1) Like _marble_ to receive and like _marble_ to retain. (2) Like _wax_ to receive and like _wax_ to retain. (3) Like _marble_ to receive and like _wax_ to retain. (4) Like _wax_ to receive and like _marble_ to retain.
The first type gives us those who memorize slowly and with much heroic effort, but who keep well what they have committed. The second type represents the ones who learn in a flash, who can cram up a lesson in a few minutes, but who forget as easily and as quickly as they learn. The third type characterizes the unfortunates who must labor hard and long for what they memorize, only to see it quickly slipping from their grasp. The fourth type is a rare boon to its possessor, enabling him easily to stock his memory with valuable material, which is readily available to him upon demand.
The particular type of brain we possess is given us through heredity, and we can do little or nothing to change the type. Whatever our type of brain, however, we can do much to improve our memory by obeying the laws upon which all good memory depends.
