Psychology 2135A/B Chapter Notes - Chapter 4: Cognitive Load, Memory Span, Decay Theory

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Chapter 4: Short-Term Working Memory10/16/2012 10:34:00 AM
George Miller: “The Magical Number 7”
FORGETTING
Rate of Forgetting
Peterson and Peterson study: tested undergrads on their ability to remember
3 consonants over a short retention interval.
E.g. subject heard the letters CHJ followed by the number 506. They would
then count backward until a light presented, which was a signal for recalling
the three consonants (the counting down from 506 by 3s disabled any verbal
rehearsal). The light went on between 3-18 sec after the subjects began
counting.
Results: probability of a correct recall declined rapidly over the 18-
second retention interval.
o Implies we must rehearse verbal info to keep it available in
STM.
o Good side about putting a phone number in STM rather than
LTM: Harder to retrieve the few numbers that you actually
regularly dial.
Decay versus Interference
Is the loss of info from STM caused by decay or interference?
Interference theory: memory for other material or the performance of
another task interferes with memory and causes forgetting.
Decay theory: info is spontaneously lost over time, even when there is no
interference from other material.
If memory decays over time, the amt of recall should be determined by the
length of the retention interval.
If memory is disrupted by interference, then recall should be determined by
the number of interfering items.
Waugh and Norman: tested whether the loss of info from STM is caused
by decay or interference.
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- presented lists of 16 single digits. The last digit in every list occurred. The
task was to report the digit that had followed the probe digit.
They varied the # of interfering items by varying the location of test digit in
the list. (many interfering items if test item occurred early in the list, and
only a few if the test item occurred late in the list.
They also tested the rate of pres, to see if the prob of recalling the test difgit
would be influenced by the length of the retention interval.
Pres digits either 1 or 4 digits per second. Result: the rate of pres
had little affect.
Memory is only slightly better for the shorter retention interval.
The prob. Of recall declines rapidly as the number of interfering
items increases.
Therefore, W and N’s findings suggest: Interference, rather than decay, is
the primary cause of forgetting. Although some decay may occur, the amt of
forgetting caused by decay is way less than the amt caused by interference.
Main Point: Interference is the chief cause of forgetting!
Release from Proactive Interference
Means how interference can be reduced by decreasing the similarly
among items.
Proactive: forgetting that occurs because of interference from material
encountered BEFORE learning.
Retroactive: forgetting that occurs… material encountered AFTER learning.
Release from P I will occur by having information be dissimilar from earlier
material.
Reduction of interference thru appropriate sequencing can partly
compensate for the rapid forgetting from STM.
CAPACITY
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The Magic Number 7
Memory span task: the # of correct items that people can immediately
recall from a sequence of items.
Magic #7 also in an absolute judgment task: identifying stims that vary
along a single, sensory, continuum (e.g. varying by loudness, pitch,
intensity)
Subject’s task is to learn to identify each stim (diff levels of loudness for
e.g.) by assigning the correct label (1 being softest, 7 loudest)
The limitation was caused by the inability to keep more than about 7 sensory
values available in STM cuz of its limited capacity.
The upper limit (7 +-2) of absolute j experiments corresponds very well with
the upper limit of memory span tasks!
Miller: putting stuff in chunks helps memory
Chunks: a cluster of items that has been stored as a unit in LTM (e.g. FBI,
HMV, ACC)
Miller: The capacity of STM should be measured in chunks rather than in
individual items.
Individual Differences in Chunking
Chunking relating to how chess players reproduce the pieces on a
chessboard. This study was done by de Groot a Dutch psychologist.
Main conclusion of the study: differences in skill among novice and master
players is from diffs in perception and memory as opposed to how they
planned their moves.
Master players depended on their ability to code the pieces into
familiar groups.
o When the players viewed pieces that were placed randomly
on the board, the master players no longer had an advantage
over the weaker players, and the two groups performed about
the same.
Chase and Simon did a similar test: identified chunks that
presumably produced the superior coding ability of master players
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Document Summary

Peterson and peterson study: tested undergrads on their ability to remember. E. g. subject heard the letters chj followed by the number 506. They would then count backward until a light presented, which was a signal for recalling the three consonants (the counting down from 506 by 3s disabled any verbal rehearsal). The light went on between 3-18 sec after the subjects began counting. Results: probability of a correct recall declined rapidly over the 18- second retention interval: implies we must rehearse verbal info to keep it available in. Stm: good side about putting a phone number in stm rather than. Ltm: harder to retrieve the few numbers that you actually regularly dial. Interference theory: memory for other material or the performance of another task interferes with memory and causes forgetting. Decay theory: info is spontaneously lost over time, even when there is no interference from other material.

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