Forgetting

1. 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

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

3. 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

4. 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

5. Trace Decay • Reitman (1974) • 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

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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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