Explanations for forgetting: interference

• Proactive interference

  Previously learnt (old) information interferes with the new information you are trying to store
• Retroactive interference

  A new memory interferes with older ones
• Interference

  One memory disturbs the ability to recall another. This might result in forgetting or distorting one or the other or both. This is more likely to happen if the memories are similar.
• Proactive interference was coined by Brenton Underwood who analysed the findings from a number of studies and concluded that when ppts have to learn a series of lists of words, they do not remember the ones encountered later on in the series as well as lists of words encountered earlier on.
• Retroactive interference was coined by Muller & Pilzecker (1900). They gave ppts a list of nonsense syllables to learn for 6 minutes, then they were given a retention interval and then asked ppts to recall the list. Performance was less good if ppts had been given the intervening task because it interfered with what they had previously learned.
• Underwood and Postman

  • Aim: investigating retroactive interference
  • Procedure: Group A were asked to learn a list of word pairs i.e. cat-tree, they were then asked to learn a second list of word pairs where the second paired word was different i.e. cat-glass. Group B were asked to learn the first list of word pairs only. Both groups were asked to recall the first list of word pairs.
  • Results: Group B recall of the first list was more accurate than the recall of group A
  • Conclusion: New learning affects the recall of old learning
• Baddeley & Hitch

  • They asked rugby players to recall the names of teams recently played.
  • However, for various reasons e.g injury, not all players had played every match.
  • This means that the players who missed matches would have less (similar) interference meaning their recall would be better than those who had played every match.
  • Those who had played in all matches were experiencing retroactive interference because their most recent games were interfering with the less recent games and therefore provides evidence to support retroactive interference.
• Keppel & Underwood

  • They asked participants to recall consonant trigrams after varying intervals, during which they counted backwards in 3s.
  • They found that, while forgetting was found to increase with the interval, there was little or no forgetting of trigrams from the start of the procedure.
  • These results can be explained in terms of proactive interference - earlier memory for the consonants had entered into the long term memory and was interfering with the memory for the later consonants.
• A strength of the interference theory as an explanation for forgetting is that most of the evidence supporting this theory comes from lab studies i.e. Underwood and Postman. This is a strength as the extraneous variables can be controlled and these experiments can be replicated  so reliability can be tested. This strengthens the theory as it gives it validity.
• A weakness of the interference theory as an explanation of forgetting is that many of its supporting studies use artificial stimuli. For example, Underwood and Potsman’s use of word pairs to investigate retroactive interference which are meaningless to the participants. So, they do not represent every day situations when we have to remember things which have meaning to us i.e. a shopping list. This weakness the theory as it brings into question its validity when explaining forgetting in everyday life.
• A weakness of interference theory as an explanation for forgetting is that some people are less affected by proactive interference than others. Kane & Engle (2000) found that people with a greater working memory were less impacted by proactive interference. This is because having a greater working memory span meant that participants had greater resources to consciously control processing and counteract proactive interference. This weakens the theory as it fails to address individual differences.