The researchers knew about the extensive evidence that in wakefulness, new situations and stimuli can readily prevent new memories from consolidating.
I guess such improvement occurs because we work harder at it, using more intensive rehearsal and perhaps using deliberate association strategies.
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.
The authors assumed that similar interference with memory formation could occur even after a sleep interlude.
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.