interference (explanations for forgetting)

• Interference theory

  • Interference = when two pieces of information disrupt each other
  • Forgetting occurs in LTM because we can’t get access to memories even though they are available
• proactive interference (PI) - old interferes with new

  • PI occurs when an older memory disrupts a newer one
  • Eg = a teacher learns many names in the past and can’t remember names of her current class
• retroactive interference (RI) - new interferes with old

  • RI happens when a newer memory disrupts an older one
  • eg = a teacher learns many new names this year and can’t remember the names of her previous students
• interference is worse when memories are similar

  • May be because:
  • In PI previously stored information makes new information more difficult to store
  • In RI new information overwrites previous memories which are similar
• McGeoch and McDonald, effects of similarity (procedure)

  • Participants were asked to learn a list of words to 100% accuracy (ie could recall them perfectly)
  • Then they were given a new list to learn. The new material varied in the degree to which it was similar to the old:
  • Group 1 = synonyms
  • Group 2 = antonyms
  • Group 3 = unrelated
  • group 4 = consonant syllables
  • Group 5 = three-digit numbers
  • Group 6 = no new list (control condition)
• McGeoch and McDonald, effects of similarity (findings/conclusions)

  • Performance depended on the nature of the second list
  • the most similar material (synonyms) produced the worst recall
  • This shows that interference is strongest when the memories are similar
• strength = some support for interference in real-world situations

  • Baddeley and Hitch = asked rugby players to recall the names of teams they had played against during a rugby season
  • Players did not play the same number of games (injuries) = those who played most (most interference) had poorest recall
  • This shows that interference operates in some everyday situations, increasing the validity of the theory
• counterpoint to support in real-world situations

  • interference in everyday situations is unusual becuase the necessary conditions are relatively rare (eg similarity of memories/learning does not occur often
  • => most everyday forgetting may be better explained by other theories (eg retrieval failure due to lack of cues)
• limitation = interference effects may be overcome using cues

  • Tulving and Psotka = gave participants lists of words organised into categories (not told what they were)
  • Recall of first list was 70% but fell with each new list (interference)
  • When given a cued recall test (names of categories) recall rose again to 70%
  • Shows interference causes just a temporary loss of access to material still in LTM - not predicted by theory
• strength = support from drug studies

  • Material learned just before taking diazepam recalled better than a placebo group one week later (retrograde facilitation)
  • The drug stopped new information reaching brain areas that process memories, so it could not retroactively interfere with stored information
  • Shows that forgetting is due to interference - reducing the interference reduced the forgetting
• extra evaluation = validity issues

  • Lab studies of interference have tight control of confounding variables (eg time) => clear link between interference and forgetting (high internal validity)
  • BUT = most research is unlike everyday forgetting (low external validity)
  • In everyday life we often earn something and recall it much later (eg revising for exams)
  • Means that because research is mostly lab-based it may overestimate the importance of of interference as a cause of forgetting