Individual Topic - Memory
FORGETTING
Definition
“The inability to recall or recognise something
that has previously been learned. This may be
due to a lack of availability, as in the case of
decay when the information has disappeared; or
may be due to a lack of accessibility, as in the
case of cue-dependent forgetting when the
memory is stored somewhere but can’t be
found at that time.” Williamson et al
Forgetting in STM
Usually explained as
information being lost from a
limited capacity and limited
duration store
Forgetting in STM
QUICK
What’s an engram?
Physical representation of information
in the brain
It is suggested that the engram disappears or
decays if it is not rehearsed. Connections
between neurons are not strengthened so …
Explains Peterson and Peterson (1959) where no
rehearsal was permitted and info had
disappeared from STM after 18 seconds at most.
BUT . . .
• How can we be sure decay took place?
• The information could have been pushed out
by new information. In P and P, the digits
participants were counting may have
DISPLACED the original nonsense trigrams.
Reitman – support for decay
• 1974
• Gave participants a different task in the
retention internal (listening for a tone).
• Attention was diverted – no rehearsal – but no
new information.
• 15 second interval recall for words dropped by
24%, evidence for decay BUT can’t be sure
new information did not enter STM while
listening to the tone.
DISPLACEMENT THEORY
STM has limited capacity so new
information overwrites the older
information.
Waugh & Norman 1965
Used rate of presentation as a measure
Decay – slower speed, would expect it to be
harder to recall early information
Displacement – rate of presentation would have
no impact
CONCLUSION
Most forgetting in STM can be explained
by displacement and some forgetting is
due to decay.
BUT . . . LTM
Has unlimited capacity and duration so why do
we forget???
Decay theory
Lashley (1931)
Rats
Mazes
Removed sections of rat brains
Found relationship between removal and
forgetting, evidence for physical decay
Decay can’t explain LTM forgetting
WHY NOT?
Possible that regular usage prevents decay – as
with STM, difficult to distinguish between decay
and displacement/interference
Baddeley & Hitch Again
But this time a natural experiment , testing
recall of rugby fixtures over a season – some
players played all games, some missed games
due to injury
Those who played more, forgot more:
Findings supported interference theory
Interference theory & LTM
Interference: tendency for one memory to
interfere with the accurate retrieval of a similar
memory
Proactive interference (PI): past learning
interferes with current attempts to learn
something
Retroactive interference (RI): Current attempts
to learn something interfere with past learning
Underwood, 1957
Lists of word pairs: cat-tree candle-whale
Then another list: cat-stone candle-cloth
Then first word is given and participant asked to
recall word from final list (PI) or from the first list
(RI)
Interference DOES cause forgetting but only
when the same stimulus is paired w/ 2 different
responses (Rare in everyday life).
Cue dependent forgetting
• It’s all there in LTM but not accessible unless a
specific cue triggers it
• Favourite childhood smells?
• The reason it would be useful to have learning
and exams in the same room!
Kinds of cueing
• External: context dependent learning (or
forgetting) , e.g., You look at a poster that
reminds you of a lesson on the cognitive
approach
• Internal: state dependent learning
Goodwin et al (1969) and the drinkers – what
they learned when drunk was forgotten when
sober but recalled when drunk again; could also
be that a song reminds you of a mood
Interference or lack of cues?
Repression & motivated forgetting
• Freudian
Repression and suppression