For 20 minutes during the break after the first study session, the odor cue was presented with the intent of helping to reactivate the memory of the first session.
To test the idea, they asked 24 volunteers to memorize the two-dimensional loca-tion of 15 pairs of cards with pictures of animals and everyday objects.
At least two processes seem to be at work: 1) sleep protects new memories from disruption by the interfering experiences that are inevitable during wakefulness, and 2) sleep consolidates memories according to their relative importance and the learner's expectations for remembering.
A good illustration of reducing interference comes from a study of napping at the University of Lübeck in Germany.
This second task was to act as an interfering disruptor of the initial learning.
The difference is that after the first memorization session, half of the group stayed awake and the other half took a nap.