Up to now, we have been outlining what may be termed the philosophical basis
for this book. In this section, we shall turn to something more concrete, and lay
out a relatively simple, overall theory of how memory operates. In subsequent
chapters, each component of the theory is examined in some detail.
The theory we shall discuss has been advanced in one form or another by a
number of psychologists (for example Waugh & Norman. 1965; Glanzer,
1972) and was described in its most complete form by Richard Atkinson and
Richard Shiffrin (Atkinson & Shiffrin, 1968, 1971). Atkinson and Shiffrin
formulated the theory as a mathematical model; this meant that the theory's
assumptions took the form of mathematical equations and that it made specific,
quantitative predictions about the outcomes of various experiments. For our
purposes, however, the mathematics may be bypassed and the theory discussed
qualitatively.
Figure 1.3 represents a schematic (and somewhat oversimplified) view of the
memory and information-processing system according to this theory. The boxes
represent “stores” or repositories of information; the arrows represent the flow
« of information from place to place. To see how the system works, imagine that

Loss of information    Loss of information
within about 1 second    within about 15 seconds
FIGURE 1.3 A schematic view of ihc two-store memory system.
you look up a telephone number, such as 325-5606. Let us trace the course of
this information as it makes its way through the system.
The information first enters the system through one of your sense organs. In
this case, the number is presented to you visually, so it enters through your
eyes. The first store into which the information is placed is called sensory
store. Sensory store can hold a large amount of information; in fact, it holds
virtually all the information impinging on a particular sense organ. If you have
looked up the number in the telephone directory, therefore, not only 325-5606
but all the other information on the page of the directory enters sensory store.
However, information in sensory store decays away very quickly—in most
cases, within a second or so. Therefore, unless information in sensory store is
quickly transferred somewhere else, it will be lost.
Some of the information in the sensory store is indeed transferred into the
next store, which is called short-term store. Short-term store (which may.be
introspectively equated with consciousness) has several major characteristics.
First of all, it is of a limited capacity; it is large enough to hold one telephone
number, but probably not large enough to hold two. Second, information in
short-term store is,  in general, lost within about 15 seconds: we have all had
the experience of looking up a telephone number and walking across the room
lo dial it, only to discover that the number has been lost by the time we reached
the telephone. However, information in short-term store may be placed into a
special section of short-term store called a rehearsal buffer. Information in the
rehearsal buffer does not decay away but may be maintained indefinitely via the
process of rehearsal. Rehearsal means just what you think it means—that
information is repeated over and over. So if you entered the number 325-5606
into your rehearsal buffer, you can maintain it by repeating to yourself
“325-5606, 325-5606 . . for as long as you wish.

Which information gets entered into the rehearsal buffer? The theory' as-
sumes that people have the ability to enter whichever information they wish

into the rehearsal buffer, allowing other information to decay away from
short-term store. The choice of which information is to be entered and which is
to be lost is presumably made in such a way that the person can carry out
whatever task he is trying to do. So, for example, when you look up a person's
number in the telephone directory, you may also find the person's address. If
you wanted to call the person up, you would enter the number into your
rehearsal buffer and allow the address to decay away. If, however, you
intended to write the person a letter, it would be more prudent to enter the
address into the rehearsal buffer and allow the number to decay away.
The final component of our system is long-term store. Long-term store is the
virtually unlimited-capacity store of that information which we have more or
less permanently available to us. For example, our own names, the multiplica-
tion table, our ability to speak a language, the days of the week, and so on are
all stored in long-term store. How does all this information get into long-term
store? It is assumed that while information resides in short-term store it can be
copied or transferred into long-term store. The longer some particular informa-

tion resides in short-term store, the more ot that information can be transferred
into long-term store. If you sit around repeating “325-5606” over and over to
yourself, you are maintaining it in short-term store. Additionally, during this
time, information about the number may be transferred to long-term store. In
everyday language, you can memorize the number.
Suppose now you are called on to retrieve some information that has
previously been presented to you—for example, suppose you have to dial the
number you have looked up. You first check to see whether that information is
in short-term store. If it is in short-term store, that's fine: you simply retrieve
the information and use it. If the information is not in short-term store, you
don’t despair yet, for the information may have resided in short-term store long
enough for it to be completely transferred to long-term store. Therefore, if the
information is not in short-term store, you next search long-term store, and if
the information is there it can be retrieved and used. (Retrieval and utilization
of information from long-term store essentially consists of transferring informa-
tion from long-term store to short-term store. This is represented by the arrow
pointing left in Figure 1.3.) It is possible of course, that some but not all of
the information has been transferred to long-term store. Thus, you may
remember the exchange, 325, but not the rest. You may remember 325-560-,
and remember that the last digit was even. You may have transferred the
information corresponding to the digits themselves but not the information
about their order, in which case you may retrieve the number 325-6506 and dial
a wrong number.
This, then, is a very brief sketch of how the memory system is assumed to
operate. The type of memory system we have described is often referred to as a
two-store system in reference to its two major information stores, short-term

store and long-term store. For each of the stores, we shall be concerned with
four major questions:
1.    How is information represented in the store?
2.    How is information lost (forgotten) from the store?
3.    How is information retrieved from the store?
4.    How is information transferred from store to store; what types of
recoding take place during transfer of information: and what, if any, informa-
tion is lost when the information is recoded?

En general, la memòria a curt termini es perd en uns 15 segons: tots hem tingut
L'experiència de buscar un número de telèfon i caminar per l'habitació
Marqueu-lo, només per descobrir que el nombre s'ha perdut en el moment que arribem
el telèfon. No obstant això, la informació en memòria a curt termini es pot col · locar en una
Secció especial de memòria de curt termini anomenada tampó d'assaig. Informació a la
El tampó d'assaig no es desfà, però es pot mantenir indefinidament a través de la
Procés d'assaig. L'assaig significa el que creieu que significa: això
La informació es repeteix una i altra vegada. Així que si heu introduït el número 325-5606
A la memòria intermèdia d'assaig, podeu mantenir-la repetint-se a vosaltres mateixos
"325-5606, 325-5606. . Durant el temps que desitgi.