Underwood

• Investigated if interference used paired associate technique
• PTS learn two word lists where first word is same in each list
• PTS learn list A till they can recall the second word in each pair when presented with first word
• If you trust recall of list B performance is affected and PTS remember words from list A by mistake
• This is an example of proactive interference because information learnt first was interfering with later material.
• If you test recall of list A performance is affected and PTS will recall words from list B by mistake. This is an example of retroactive interference as new memory is displaced with old memory.