If you show a chess grand master
a chessboard on which a game is in progress, he can memorize the exact positions
of all the pieces in just a few seconds. But if you take the same number of pieces,
distribute them at random positions on the chessboard, then ask him to memorize
them, he will do no better than you or I. Why? Because in the first case, he uses
his excellent knowledge of the rules of the game to quickly eliminate any positions
that are impossible, and his numerous memories of past games to draw analogies
with the current situation on the board.
MEMORY AND LEARNING
Learning is a process
that lets us retain acquired information, affective states, and impressions that
can influence our behaviour. Learning is the main activity of the brain, in which
this organ continuously modifies its own structure to better reflect the experiences
that we have had.
But memory is not
entirely faithful. When you perceive an object, groups of neurons in different
parts of your brain process the information about its shape, colour, smell, sound,
and so on. Your brain then draws connections
among these different groups of neurons, and these relationships constitute
your perception of the object. Subsequently, whenever you want to remember the
object, you must reconstruct these relationships. The parallel processing that
your cortex does for this purpose, however, can alter your memory of the object.
Also, in your brain's memory systems, isolated pieces
of information are memorized less effectively than those associated with existing
knowledge. The more associations between the new information and things that you
already know, the better you will learn it. For example, you will have an easier
time remembering that the entorhinal cortex is connected to the hippocampus via
the dentate gyrus if you already have some basic knowledge of brain anatomy.
Psychologists have identified a number of factors that can influence how effectively
of vigilance, alertness, attentiveness, and concentration
Attentiveness is often said to be the tool that engraves information into
memory. Thus, attention deficits can radically reduce memory performance. You
can improve your memory capacity by making a conscious effort to repeat and integrate
Interest, strength of motivation, and need or necessity
It is easier
to learn when the subject fascinates you. Thus, motivation is a factor
that enhances memory. Some young people who do not always do very well at the
subjects they are forced to take in school often have a phenomenal memory for
statistics about their favourite sports.
Affective values associated with the material to be memorized, and the individual’s
mood and intensity of emotion
Your emotional state when an event
occurs can greatly influence your memory of it. Thus, if
an event is very upsetting, you will form an especially vivid memory of it.
For example, many people remember where they were when they learned about President
Kennedy’s assassination, or about the attacks of September 11, 2001. The
processing of emotionally-charged events in memory involves norepinephrine, a
neurotransmitter that is released in larger amounts when we are excited or tense.
As Voltaire put it, that which touches the heart is engraved in the memory.
Location, light, sounds, smells...in short, the entire context in which the memorizing
takes place is recorded along with the information being memorizes.
Our memory systems are thus contextual. Consequently, when you have trouble
remembering a particular fact, you may be able to retrieve it by recollecting
where you learned it or the book from which you learned it. Was there a picture
on that page? Was the information toward the top of the page, or the bottom? Such
items are called “recall indexes”. And because you always memorize
the context along with the information that you are learning, by recalling
this context you can very often, by a series of associations, recall the information
Forgetting is another important
aspect of memorization phenomena. Forgetting lets you get rid of the tremendous
amount of information that you process every day but that your brain decides it
will not need in future.
"The purpose of memory is not to let us recall
the past, but to let us anticipate the future. Memory
is a tool for prediction."
- Alain Berthoz
Baddeley, a specialist in working memory, proposes a model of working memory
with several components: a control system, a central processor, and a certain
number of auxiliary “slave” systems. One of these slave systems, the
phonological or articulatory loop, specializes in processing linguistic information,
while another specializes in processing visuo-spatial information.
The phonological or articulatory loop plays
an important role in everyday life. For example, when you repeat a phone number
to yourself in your head, you are activating this loop. This loop is also heavily
involved in reading and writing. The presence in working memory of another slave
system that can manipulate mental images of visual objects is suggested by tests
where subjects are asked to rotate such images. Perhaps the most important but
least understood component in Baddeley’s model of working memory is the
central processor, whose job would be to select, initiate, and halt the routines
performed by its slave systems.
SENSORY, SHORT-TERM AND LONG-TERM MEMORY
is the memory that results from our perceptions automatically and generally disappears
in less than a second. It includes two sub-systems: iconic memory of visual perceptions
and echoic memory of auditory perceptions.
memory depends on the attention paid to the elements of sensory memory. Short-term
memory lets you retain a piece of information for less than a minute and retrieve
it during this time. One typical example of its use is the task of repeating a
list of items that has just been read to you, in their original order. In general,
you can retain 5 to 9 items (or, as it is often put, 7±2 items) in short-term
Working memory is a more
recent extension of the concept of short-term memory. As techniques for studying
memory have become more refined, it has become increasingly apparent that the
original conception of short-term memory as a mere temporary receptacle for long-term
memory is too simplistic. In fact, it is becoming increasingly clear that there
is no strict line of demarcation between memories and thoughts. In order to test
some hypotheses that may provide a better understanding of this complex phenomenon,
the concept of working memory has therefore been advanced.
Working memory is used
to perform cognitive processes on the items that are temporarily stored in it.
It would therefore be heavily involved in processes that require reasoning, such
as reading, or writing, or performing computations. One typical example of the
use of working memory is the task of repeating a list of items that has just been
read to you, but in the reverse of their original order. Another good example
is the task of simultaneous interpretation, where the interpreter must store information
in one language while orally translating it into another.
memory appears to be composed of several independent systems, which would imply
that we are not aware of all the information that is stored in it at any given
time. For example, when you drive a car, you are performing several complex tasks
simultaneously. It is unlikely that all of the various types of information involved
are being handled by a single short-term memory system.
Long-term memory includes both our memory
of recent facts, which is often quite fragile, as well as our memory of older
facts, which has become more consolidated. Long-term memory consists of three
main processes that take place consecutively: encoding, storage, and retrieval
(recall) of information.
The purpose of encoding is
to assign a meaning to the information to be memorized. For example, you might
encode the word "lemon" as “fruit, roundish, yellow”. If
you could not recall the word “lemon” spontaneously, then invoking
one of the indexes that you used to encode it (such as “fruit”) should
help you to retrieve it. How effectively you can retrieve information depends
on how deeply you have encoded it, and hence on how well you have organized it
in your memory. The process of encoding refers not only to the information being
memorized, but also to its environmental, cognitive, and emotional context. Also,
devices to associate ideas and images helps us to create links that facilitate
encoding. (One classic example is the acrostic Every Good Boy Deserves Favour,
for the musical notes on the lines of the treble clef.) But even when information
has been well encoded, it can still be forgotten.
Storage can be regarded as the active process of consolidation that makes memories
less vulnerable to being forgotten. It is this consolidation that differentiates
memories of recent facts from memories of older ones. The latter have been associated
with a larger amount of pre-existing knowledge. Sleep, and in particular the rapid-eye-movement
(REM) phase of sleep, along with reviewing (such as studying for exams) play a
large role in consolidation.
Lastly, retrieval (recall)
of memories, whether voluntary or not, involves active mechanisms that make use
of encoding indexes. In this process, information is temporarily copied from long-term
memory into working memory, so that it can be used there. The more a memory has
been encoded, elaborated, organized, and structured, the easier it will be to
retrieve. Thus, we see that forgetting can be caused by failures at any of
these stages: poor encoding, insufficient consolidation, or difficulties in retrieval.
of information encoded in long-term memory is traditionally divided into two categories:
recall and recognition. Recall involves actively reconstructing the information,
whereas recognition only requires a decision as to whether one thing among others
has been encountered before. Recall is more difficult, because it requires the
activation of all the neurons involved in the memory in question. In contrast,
in recognition, even if a part of an object initially activates only a part of
the neural network concerned, that may then suffice to activate the entire network.
Semantic memory can be regarded as the residue
of experiences stored in episodic memory. Semantic memory homes in on common features
of various episodes and extracts them from their context. A gradual transition
takes place from episodic to semantic memory. In this process, episodic memory
reduces its sensitivity to particular events so that the information about them
can be generalized.
Conversely, our understanding of
our personal experiences is necessarily due to the concepts and knowledge stored
in our semantic memory. Thus, we see that these two types of memory are not isolated
entities, but rather interact with each other constantly.
In Alzheimer’s disease, patients quickly develop
difficulty in retrieving individual words and general knowledge. Studies have
shown that in tasks such as describing and naming items, these patients display
a loss of knowledge of the specific characteristics of semantic categories. Initially,
they lose the ability to distinguish fine categories, such as species of animals
or types of objects. But over time, this lack of discrimination extends to broader,
more general categories. At first, if you show such patients a spaniel, they may
say, “that is a dog”. Later, they may just say “that is an animal”.
DIFFERENT TYPES OF LONG-TERM MEMORY
As the diagram below
shows, long-term memory can be divided into explicit
and implicit memory, and implicit memory can in turn be divided into various
subtypes. But always bear in mind that in the actual workings of human memory,
these various subsystems are interacting all the time. The interactions between
episodic and semantic memory-two distinct forms of explicit memory-may offer the
best example (see sidebar).
memory (sometimes called autobiographical memory) lets you remember events
that you personally experienced at a specific time and place. It includes memories
such as the meal you ate last night, or the name of an old classmate, or the date
of some important public event.
The most distinctive
feature of episodic memory is that you see yourself as an actor in the events
you remember. You therefore memorize not only the events themselves, but also
the entire context surrounding them.
is the kind most often affected by various forms of amnesia. Also, the emotional
charge that you experience at the time of the events conditions the quality of
your memorization of the episode.
memory is the system that you use to store your knowledge of the world. It
is a knowledge base that we all have and much of which we can access quickly and
effortlessly. It includes our memory of the meanings of words–the kind of
memory that lets us recall not only the names of the world’s great capitals,
but also social customs, the functions of things, and their colour and odour.
Semantic memory also includes our memory of
the rules and concepts that let us construct a mental representation of the world
without any immediate perceptions. Its content is thus abstract and relational
and is associated with the meaning of verbal symbols.
memory is independent of the spatial/temporal context in which it was acquired.
Since it is a form of reference memory that contains information accumulated repeatedly
throughout our lifetimes, semantic memory is usually spared when people suffer
from amnesia, but it can be affected by some forms of dementia (see sidebar).