Forgetting The inability to recall or recognise something that was previously learned In short-term memory Decay Decay Displacement Displacement In long-term memory Interference Interference Cue dependent forgetting Cue dependent forgetting

Trace Decay (STM)

Trace Decay Trace decay Based on the idea that information is physically represented as a memory trace (i.e. arrangement of neurones) 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 The trace is fragile and disintegrates if not constantly refreshed After about 20s, the trace has decayed completely & recall is no longer possible After about 20s, the trace has decayed completely & recall is no longer possible

Trace Decay Peterson & Peterson (1959) Recall of trigrams after varying intervals Recall of trigrams after varying intervals Interference task to prevent rehearsal Interference task to prevent rehearsal Found less that 10% recall after 18s Claimed evidence for decay in STM Claimed evidence for decay in STM However, interference task might have caused displacement of trigrams However, interference task might have caused displacement of trigrams

Trace Decay Reitman (1974) Attempt to avoid the confounding effects of displacement Attempt to avoid the confounding effects of displacement Used a tone detection task instead of a verbal interference task Used a tone detection task instead of a verbal interference task Found recall declined by 24% over 15s Claimed evidence for decay Claimed evidence for decay Seems to occur more slowly than Peterson & Peterson suggested Seems to occur more slowly than Peterson & Peterson suggested

Displacement (STM) Short Term Memory

Displacement Displacement Based on the idea that STM has a strictly limited capacity for information 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 If STM is full and new information is registered, then some existing info is pushed out or overwritten

Displacement Waugh & Norman (1965) PPs heard a list of 16 digits 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 They were then told one of the digits and had to repeat the one that came after it Recall was better when the PPs were recalling from the end of the list Consistent with earlier digits being displaced by later ones Consistent with earlier digits being displaced by later ones Agrees with other findings (recency effects) Agrees with other findings (recency effects)

Displacement Shallice (1967) Repeated Waugh & Norman’s study but varied the rate of presentation of the digits Repeated Waugh & Norman’s study but varied the rate of presentation of the digits Found better recall when digits were presented faster Challenges displacement, as number of bits of info was the same Challenges displacement, as number of bits of info was the same Supports decay as faster-presented digits had less time to decay Supports decay as faster-presented digits had less time to decay

Forgetting in STM Forgetting in STM is affected by: Amount of information presented Amount of information presented Rate of presentation Rate of presentation Interval between presentation & recall Interval between presentation & recall Task demands 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)