Explanations for forgetting: Interference

Müller + Pilzecker (1900) 1st to identify RI. Gave participants list of nonsense syllables to learn for 6 mins, then after retention interval, asked to recall. Performance less good if participants been given intervening task b/ween initial learning + recall (shown 3 landscape paintings + asked to describe them).

Intervening task produced RI b/c later task interfered w/ what previously learned. New interferes w/ old. 

Underwood (1957) showed PI could be equally significant. Analysed findings from number of studies, concluded when participants learn series of word lists, don't learn list of words encountered later on in sequence as well as lists of words encountered earlier on.

Overall, found if memories 10+ lists, after 24 hours, remembered 20% of what learned. If only learned 1 list, recall over 70%. Old intereferes w/ new.

McGeoch + McDonald (1931) gave participants list of 10 adjs (List A) - once learned, resting interval 10 mins where learned List B, then recall.

If List B list of synonyms of List A, recall poor (12%). If List B nonsense syllabus, less effect (26% recall). If List B numbers, had least effect (37% recall). Shows interference strongest more similar items are. Only interference, rather than decay, that can explain these effects.

Baddeley + Hitch (1977) - investigated interference effect in everyday setting - rugby players recalling names of teams played against over rugby season. Some players played in all games, some missed some b/c of injury. Time of interval from start-end of season same for all players, but number of intervening games diff for each player b/c of missed games.

If decay theory correct, all players should recall similar % games place b/c time alone should -> forgetting. If interference theory correct, players who played most fames should forger proportionately more b/c of interference - what Baddeley + Hitch found. Demonstrates interference in everyday life.

Danaher et al (2008) - found recall + recognition of advertiser's message impaired when participants exposed to 2 advertisements for competing brands w/in week. Serious problem considering amount of money advertisers spend only to have effect of advertisement diluted by interference. D suggests 1 strategy might be enhance memory trace by running multiple exposures to advert on 1 day rather than spread out over week. Results in reduced interference from competitors' adverts.

Real world rugby study.

Research artificial - lab-based, artificial list of words and/or nonsense syllables. Findings may not relate to everyday uses of memory. Participants may lack motivation to remember links - may allow interference effects stronger than really are - lack ecological validity.

Accessibility vs availability - questioned whether interference causes memory to disappear or just temp. Ceraso (1967) found if memory tested again after 24 hours, recognition (accessibility) showed considerable spontaneous recovery. Recall (availability) remained same. Suggests interference occurs b/c temp unaccessible rather than being lost.

Individual diffs - evidence some less affected by PI. Kane + Engle (2000) - showed individuals w/ greater working memory span less susceptible to PI. Researchers tested by giving participants 3 word lists to learn. Low WM spans - greater PI when recalling 2nd + 3rd lists than did participants w/ higher spans. Further test - greater WM span meant greater resources to consciously control processing + counteract effects of PI.