OVERCOMING THE PROBLEM USING MEMORY

To address this problem, memory is often studied by comparing two groups of participants or information, organized such that the ‘past event’ occurs for one group but not for the other. Because the only known difference between the groups is the presence or absence of the event, differences observed at the later time are assumed to reflect memory for that event. It is therefore essential to determine that there are no other differences between the groups. The sleep learning experiment Suppose you played tapes of information to yourself in your sleep. Would you remember the information later? (For a review of ‘sleep learning’, see Druckman & Bjork, 1994.) To answer the question, you might present some information to people while they sleep, wake them up, and then observe whether their subsequent behaviour reflects any memory for that information. Wood, Bootzin, Kihlstrom and Schacter (1992) did just this. While people slept, the researchers read out pairs of category names and member names (e.g. ‘a metal: gold ’), repeating each pair several times. After ten minutes, the sleepers were awakened and asked to list members of named categories – such as metals – as they came to mind. The assumption was that if participants had any memory for having ‘a metal: gold’ read to them while they slept, then they would be more likely to include gold in their list of metals.