5. Interference theory

• What is interference?

  • Forgetting a piece of information because one memory blocks another, causing one or both memories to be distorted or forgotten
• Interference theory

  • Occurs when two pieces of information disrupt each other, resulting in forgetting one memory or both
  • Proposed mainly as an explanation for forgetting LTM - forgetting is most likely because we can't gain access to them even though they are available. Makes memories hard to locate
• Types of interference

  • Proactive - when older memories disrupt the recall of newer memories. The degree of forgetting is greater when the memories are similar. Eg. teacher can't remember names in her new class due to having so many previous classes/students
  • Retroactive - when newer memories disrupt the recall of older memories. The degree of forgetting is again greater when the memories are similar. Eg. a teacher learning so many new names that she has difficulty remembering previous students names
• Research on the effects of similarity

  • McGeoch and Mcdonald studied retroactive interference by changing the amount of similarity between two sets of materials.
  • Pps had to learn a list of 10 words until they could recall them with 100% accuracy. They then learnt a new list
  • Group 1 - synonyms (produced worst recall)
  • Group 2 - antonyms
  • Group 3 - words unrelated to the original ones
  • Group 4 - consonant syllables
  • Group 5 - three-digit numbers
  • Group 6 - control condition with no new list
• Explanation of the effects of similarity

  • Proactive interference - previously stored info makes new similar info more difficult to store
  • Retroactive interference - new info overwrites previous similar memories because of the similarity
• Strength - evidence of interference effects in real life

  • Baddely and Hitch asked rugby players to recall the names of teams they had played against during a rugby season - all played for the same time interval but the number of intervening games varied due to some missing matches for injuries
  • Players who played the most games had the poorest recall
  • Shows interference theory can operate in real life, making it generalisable and having high ecological validity
• Counterpoint - unusual for interference to occur in real life

  • Conditions for interference to occur are relatively rare
  • This is unlike lab studies where the high degree of control means a researcher can create ideal conditions for interference
  • Memories have to be fairly similar in order to interfere with each other and may happen occasionally but not often eg. revising similar subjects close in time
  • Suggests forgetting may be better explained by theories such as retrieval failure
• Strength - evidence of retrograde facilitation

  • Coenen gave pps a list of words and later asked them to recall the list assuming the intervening experiences would act as interference
  • They found when pps were under the influence of diazepam, recall one week later was poor compared to a placebo control group. When the list was learnt before the drug was taken, later recall was better than the placebo - the drug improved recall of material
  • Wixted suggests the drug prevents new information reaching parts of the brain involved in processing memories - RI cannot happen with memories already stored
• Limitation - interference is temporary and can be overcome by using cues

  • Tulving and Psotka gave pps lists of words organised into categories, one list at a time
  • Recall averaged about 70% for the first list, but became progressively worse as pps learned each additional list (PI)
  • Had words really left LTM or were they still available?
  • At the end of the procedure pps were given a cued recall test - told the names of the categories and recall rose again to 70%
  • Shows interference causes a temporary loss of accesibility to material still in LTM