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

Trace Decay (STM) www.psychlotron.org.uk

Trace Decay Trace decay 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 www.psychlotron.org.uk

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

Trace Decay Reitman (1974) Found recall declined by 24% over 15s 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 Claimed evidence for decay Seems to occur more slowly than Peterson & Peterson suggested www.psychlotron.org.uk

Displacement (STM) Short Term Memory www.psychlotron.org.uk

Displacement Displacement 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 www.psychlotron.org.uk

Displacement Waugh & Norman (1965) 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 Recall was better when the PPs were recalling from the end of the list Consistent with earlier digits being displaced by later ones Agrees with other findings (recency effects) www.psychlotron.org.uk

Displacement Shallice (1967) 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 Supports decay as faster-presented digits had less time to decay www.psychlotron.org.uk

Forgetting in STM Forgetting in STM is affected by: 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) www.psychlotron.org.uk

Forgetting in LTM Availability vs accessibility (DEFINE THESE CAREFULLY) Interference Suggests that information forgotten from LTM has disappeared completely Cue dependent forgetting Suggests that forgotten information is still stored, but is (temporarily) inaccessible www.psychlotron.org.uk

Interference Forgetting occurs when information to be stored is similar to information already in LTM 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 www.psychlotron.org.uk

Interference McGeoch & MacDonald (1931) PPs had to learn lists of adjectives, recall after a delay. Three conditions: 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 www.psychlotron.org.uk

Interference Tulving (1966) PPs asked to free recall word lists they had previously learned Recall tested on several different occasions Generally, PPs recalled about 50% of the words, but not always the same 50% Suggests that words had not disappeared but had actually been inaccessible This is contrary to what interference theory suggests www.psychlotron.org.uk

Interference 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 www.psychlotron.org.uk

Cue Dependent Forgetting Forgetting occurs when information becomes inaccessible 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 www.psychlotron.org.uk

Cue Dependent Forgetting Smith (1970) tested recall of a word list in the original learning context or a different room 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 www.psychlotron.org.uk

Cue Dependent Forgetting Fair amount of support for role of state cues in forgetting/remembering e.g 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 www.psychlotron.org.uk

Cue Dependent Forgetting Much research support for basic propositions. Retrieval seems to be most likely when conditions match those of initial learning Does not apply equally to all types of info E.g. procedural memories (skills) seem stable, resistant to forgetting and not reliant on retrival cues www.psychlotron.org.uk