The Nature Of Memory
Now that you come to think of it, you can recall perfectly well that
Columbus discovered America in 1492; that your house is painted white;
that it rained a week ago today. But where were these once-known facts,
now remembered so easily, while they were out of your mind? Where did
they stay while you were not thinking of them? The common answer is,
Stored away in my memory. Yet no one believes that the memory is a
ouse of facts which we pack away there when we for a time have no
use for them, as we store away our old furniture.
WHAT IS RETAINED.--The truth is that the simple question I asked you is
by no means an easy one, and I will answer it myself by asking you an
easier one: As we sit with the sunlight streaming into our room, where
is the darkness which filled it last night? And where will all this
light be at midnight tonight? Answer these questions, and the ones I
asked about your remembered facts will be answered. While it is true
that, regardless of the conditions in our little room, darkness still
exists wherever there is no light, and light still exists wherever there
is no darkness, yet for this particular room there is no darkness when
the sun shines in, and there is no light when the room is filled with
darkness. So in the case of a remembered fact. Although the fact that
Columbus discovered America some four hundred years ago, that your house
is of a white color, that it rained a week ago today, exists as a fact
regardless of whether your minds think of these things at all, yet the
truth remains as before: for the particular mind which remembers these
things, the facts did not exist while they were out of the mind.
It is not the remembered fact which is retained, BUT THE POWER TO
REPRODUCE THE FACT WHEN WE REQUIRE IT.
THE PHYSICAL BASIS OF MEMORY.--The power to reproduce a once-known fact
depends ultimately on the brain. This is not hard to understand if we go
back a little and consider that brain activity was concerned in every
perception we have ever had, and in every fact we have ever known.
Indeed, it was through a certain neural activity of the cortex that you
were able originally to know that Columbus discovered America, that your
house is white, and that it rained on a day in the past. Without this
cortical activity, these facts would have existed just as truly, but
you would never have known them. Without this neural activity in the
brain there is no consciousness, and to it we must look for the
recurrence in consciousness of remembered facts, as well as for those
which appear for the first time.
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:
Brains that are:
(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.