Interference

• Interference = forgetting because one memory blocks another, causing one or both memories to be distorted or forgotten
• Proactive interference = when older memories disrupt the recall of newer memories (e.g. a teacher can't remember the names of her new class because she has learned so many names in the past)
• Retroactive interference = when a newer memory interferes with an older one (e.g. a teacher has learnt so many names this year she has trouble remembering the names of the students last year)
• In both proactive and retroactive interference, the interference is worse when the memories are similar (McGeoch and McDonald)
• McGeoch and McDonald studied retroactive interference by changing the amount of similarity between two sets of materials. Participants had to learn 10 words until they could remember them with 100% accuracy. They then learned a new list of words.
• McGeoch and McDonald:

  There were six groups who had to learn different types of new lists:

  • group 1: synonyms
  • group 2: antonyms
  • group 3: unrelated words
  • group 4: consonant syllables
  • group 5: 3-digit numbers
  • group 6: no new list
• McGeoch and McDonald:

  The most similar material (synonyms) produced the worst recall, when the participants were asked to recall the original list. This shows interference is strongest when memories are similar.
• The reason similarity affects recall may be for one of two reasons. Proactive interference- previously stored information makes new similar information difficult to store. Retroactive interference- new information overwrites previous similar memories because of the similarity.
• There is evidence of interference effects in more everyday situations. Baddeley and Hitch asked rugby players to recall the names of teams they had played. The players had all played for the same interval but the number of intervening games varied. Players who had played the most games had the poorest recall. This shows interference can operate in some real-world situations, increasing the validity of the theory.
• Interference may cause some forgetting in everyday situations but it is unusual as the conditions necessary for interference are relatively rare. Two memories have to be fairly similar in order to interfere with each other. This may happen occasionally in everyday life but not often. This suggests forgetting may be better explained by other theories such as retrieval failure due to a lack of cues.
• Interference is temporary and can be overcome by using cues. Tulving and Psotka gave participants lists of words organised into two categories. Recall averaged about 70% for the first list but became progressively worse as participants learned each additional list. At the end the participants were given a cued recall test- they were told the names of the categories. Recall rose to about 70% again. This shows interference causes a temporary loss of accessibility to material that is still in LTM, a finding not predicted by interference theory.
• Another strength comes from evidence of retrograde facilitation. Coenen and van Luijtelaar gave participants a list of words and later asked them to recall the list, assuming the intervening experiences would act as interference. They found that when a list of words was learned under diazepam recall a week later was poor compared to placebo. But when a list was learned before the drug was taken, later recall was better than placebo. So the drug actually improved recall of material learned beforehand. Wixted suggests this is because the drug prevents new information reaching parts of the brain involved in processing memories so it cannot interfere retroactively with information already stored. This shows forgetting can be due to interference.