Developmental psychology.pdf

240 Learning and Information Processing
seemed to be the effective maximum, and almost all subjects could recall at least five
items. The investigator was prompted to speak of the "magical number seven," noting
that we should think of it as seven plus or minus two (Miller, 1956).
This characteristic of short-term memory is both a drawback and an asset.
The drawback is obvious, for material that cannot be retained for a few seconds certainly
cannot be recalled a few hours, days, or years later. It is also a drawback in the
sense that thinking uses some of the capacity of STM, with the result that we can only
think about seven or so items at one time. But imagine the difficulties you would experience
if everything that passed through the sensory register remained in short-term
memory. You would be constantly aware of the "blooming, buzzing confusion" in our
environment, making it more and more impossible to receive and handle incoming information.
Figure 9.7
Short-Term Memory- A telephone
number is commonly seven digits,
the average short-term memory
capacity. To retain the new number
after dialing for information, we need
some moments for rehearsal.
Processing in Short- Term Memory The need to process in formation in short-term
memory, if it is to be retained, is also readily evident in daily life. Simply dial the
operator and ask for a certain telephone number. Also ask for the time or about the
weather, and try to recall the number. Unless you knew the number earlier, and just
needed a refresher for long-term memory, it is m6st likely that you cannot recall it
(Figure 9.7).
Unless the new material is vivid and simple, we need rehearsal to keep it in
short-term memory. In rehearsal, the information or task is practiced in one way or
another, covertly or overtly. The event is simply repeated several times, as in saying a
telephone number again and again. The aim here is merely to keep the material available
until it can be used, as in dialing the number, or until it can be stored in some
more integrated fashion. Napoleon, concerned about his inability to remember someone's
name, silently repeated it several times after first hearing it.
The importance of rehearsal was demonstrated when experimental subjects
were unable to remember a single nonsense syllable for just a few seconds. The experimenter
presented them with a three-letter syllable followed by a number. Each
subject observed the syllable visually and then, to prevent rehearsal, was required to
count backward by three or four from a randomly selected three-digit number. When
the subject was asked the syllable three seconds later, it was repeated correctly only
about half the time. With successively more counting, recall continued to decline, and
after 18 seconds, less than 10 percent of the syllables were recalled (Peterson & Peterson,
1959).
Long-Term Memory
In the third phase, long-term memory (LTM), information is retained for extended
intervals, defined as anything from 30 seconds to the full life of the organism, sometimes
many decades. Long-term memory is final storage, not an interim stage. It seems
to be some irreversible modification of the nervous system and has been the subject of
most memory research in psychology.
Besides the time factor, long-term memory differs from short-term memory
in two other ways. .First, it is presumed to have an unlimited capacity, or at least the
limits are not known. Short-term memory has a capacity of seven categories, give or
take two, whereas in long-term memory even the capacity for visual recognition appears
to have no discoverable limit (Standing, 1973).
Second, the mode of data processing is different in the two stages. To maintain
material in short-term memory requires simple repetition, adequate for a brief period,
but except in rare cases this process has no long-term implication. To transfer something
to the vast warehouse of long-term memory, a more elaborate system is needed.
This process, called encoding, or recoding, involves the preparation of information in
a useful way so that it can be remembered. The data are converted into a usable format.