Transcript Explanations of Forgetting 2011

Forgetting
The inability to recall or recognise
something that was previously learned
In short-term memory
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Decay
Displacement
In long-term memory
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Interference
Cue dependent forgetting
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Trace Decay (STM)
Trace Decay
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Based on the idea that information is
physically represented as a memory trace (i.e.
arrangement of neurones)
The trace is fragile and disintegrates if not
constantly refreshed
After about 20s, the trace has decayed
completely & recall is no longer possible
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Trace decay
Trace Decay
Peterson & Peterson (1959)
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Recall of trigrams after varying intervals
Interference task to prevent rehearsal
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Claimed evidence for decay in STM
However, interference task might have
caused displacement of trigrams
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Found less that 10% recall after 18s
Trace Decay
Reitman (1974)
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Attempt to avoid the confounding effects of
displacement
Used a tone detection task instead of a verbal
interference task
Found recall declined by 24% over 15s
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Claimed evidence for decay
Seems to occur more slowly than Peterson &
Peterson suggested
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Displacement (STM)
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Short Term Memory
Displacement
Displacement
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Based on the idea that STM has a strictly
limited capacity for information
If STM is full and new information is
registered, then some existing info is pushed
out or overwritten
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Displacement
Waugh & Norman (1965)
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PPs heard a list of 16 digits
They were then told one of the digits and had
to repeat the one that came after it
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Consistent with earlier digits being displaced
by later ones
Agrees with other findings (recency effects)
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Recall was better when the PPs were
recalling from the end of the list
Displacement
Shallice (1967)
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Repeated Waugh & Norman’s study but
varied the rate of presentation of the digits
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Challenges displacement, as number of bits
of info was the same
Supports decay as faster-presented digits had
less time to decay
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Found better recall when digits were
presented faster
Forgetting in STM
Forgetting in STM is affected by:
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Amount of information presented
Rate of presentation
Interval between presentation & recall
Task demands between presentation & recall
Very difficult to say whether decay or
displacement is the most important
process
Other factors also important e.g. acoustic
similarity in the info (Baddeley, 1966)
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Forgetting in LTM
Availability vs accessibility (DEFINE
THESE CAREFULLY)
Interference
Suggests that information forgotten from LTM
has disappeared completely
Cue dependent forgetting
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Suggests that forgotten information is still
stored, but is (temporarily) inaccessible
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Interference
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Retroactive - new info ‘overwrites’ previously
stored info
Proactive - previously stored info prevents
new info from being stored properly
Predicts that forgetting will increase with
similarity of information
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Forgetting occurs when information to be
stored is similar to information already in
LTM
Interference
McGeoch & MacDonald (1931)
PPs had to learn lists of adjectives, recall
after a delay. Three conditions:
2.
3.
Did nothing between learning & recall
Learned additional unrelated material
Learned additional adjectives
Most forgetting in group 3
Supports prediction that forgetting is a
function of similarity
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1.
Interference
Tulving (1966)
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PPs asked to free recall word lists they had
previously learned
Recall tested on several different occasions
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Suggests that words had not disappeared but
had actually been inaccessible
This is contrary to what interference theory
suggests
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Generally, PPs recalled about 50% of the
words, but not always the same 50%
Clearly it is possible to confuse similar
information
Some experiments support interference
theory, but they are very artificial
Information that has been forgotten often
becomes recoverable later
Unlikely that interference accounts for
most of the forgetting we do
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Interference
Cue Dependent Forgetting
Forgetting occurs when information
becomes inaccessible
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We lack the appropriate retrieval cues that will
allow us to locate it in LTM
Retrieval cues can be external (context) or
internal (state)
Predicts that remembering will be better
when state & context are the same as at
the time of learning
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Cue Dependent Forgetting
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Same room – 18/80 words
Different room – 12/80 words
PPs who imagined themselves back in
original room recalled avg. 17/80
Strong evidence for role of context cues in
retrieval
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Smith (1970) tested recall of a word list in
the original learning context or a different
room
Cue Dependent Forgetting
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Goodwin et al (1969) – heavy drinkers often
forgot where they had put things when sober,
but remembered once they had drunk
sufficient alcohol
Eich (1980) similar findings with heavy
marijuana users
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Fair amount of support for role of state
cues in forgetting/remembering e.g
Cue Dependent Forgetting
Much research support for basic
propositions.
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Retrieval seems to be most likely when
conditions match those of initial learning
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E.g. procedural memories (skills) seem
stable, resistant to forgetting and not reliant
on retrival cues
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Does not apply equally to all types of info