Interference Theory

• Background

  • Interference theory has been proposed as an explanation for forgetting in LTM
  • Interference occurs when one memory in LTM disrupts the ability to recall another memory in LTM
  • Psychologists have suggested that there are two types of interference
  • Proactive interference
  • Retroactive interference
• Proactive interference

  • Proactive interference occurs when an older memory interferes with a newer one
  • For example, a teacher has learnt so many names in the past that they have difficulty remembering the names of their current students
• Retroactive interference

  • Retroactive interference occurs when a newer memory interferes with an older one
  • For example, a teacher has learnt so many new names this year that they have difficulty remembering the names of their past students
• Effects of similarity

  • In the case of both proactive and retroactive interference, the interference is worse when the memories are similar
  • Research was conducted by McGeoch & McDonald (1931) to demonstrate this
• What were participants asked to do in the research study?

  Learn a list of 10 words until they could recall them with 100% accuracy
• How were participants divided in the study?

  They were divided into six groups
• What were the six groups in the study tasked with learning?


  1. Group 1: Synonyms
  2. Group 2: Antonyms
  3. Group 3: Unrelated words
  4. Group 4: Nonsense syllables
  5. Group 5: Three-digit numbers
  6. Group 6: Did not learn a new list
• What was the main task participants had to perform after learning the second list?

  Recall the original list of words
• What did the study find about performance in recalling the original list of words?

  Performance depended upon the nature of the second list
• Which group produced the worst recall of the original words?

  Group 1, who learnt a list of synonyms
• What conclusion did McGeoch & McDonald draw from their findings?

  Interference is strongest when memories are similar