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Peterson & Peterson (1959)
How fast does our Short-term Memory Decay?
Peterson and Peterson investigated one of the factors that
causes our short-term memory to decay, i.e. why we forget information in our
short-term memory. In 1959, they conducted an experiment that revealed how time
between remembering something and having to recall it affected the life of a
What is at Trigram, and why
Peterson and Peterson showed participants a trigram
- a set of 3 consonant letters, such as ADW. This method would be known
as the Brown-Peterson technique, and can be used to remove
a number of factors that might affect someone's memorization of a piece
1) The trigram has little or no
meaning, unlike asking a person to remember a word which they may associate
with something and be able to remember better.
2) There are no vowels in the trigram,
preventing any easy pronunciation of the trigram as a word, which makes
it more difficult to remember on any other basis than as a trigram.
3) Unlike words, the trigrams are
equal in length, making the experiment less biased in terms of the information
it requires participants to remember.
In the experiment:
Participants were asked to remember a trigram
Next, they were given a delay between recall in which
they were required to perform an interference task, which
would reduce the chances of them using techniques to rehearse the data and
remember it better. The delay between being shown the trigram and asked to
recall it varied between participants - one of the following intervals: 3,
6, 9, 12, 15 or 18 seconds.
Participants tried to recall the trigram.
Recall success was around 50% after an interval of 3 seconds
and interference task, but this reduced gradually to around 10% over intervals
of 6, 9 and 12 seconds, and gradually to around 5% success after 18 seconds.
This suggests that time does result in decay in the short
Evaluation of the Experiment
Peterson and Peterson were
careful to eliminate factors other than time that might affect recall:
reduced the chances of rehearsal before recall.
In addition to this trigrams were used to eliminate
the attached meaning that might be used to remember, for example, words,
Lacks ecological validity - how
often is a person needed to remember trigrams in reality?
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