If you were to ask a reasonably intelligent and well-informed person what caused forgetting, you might get the offhand reply, "oh, just the passage of time, I guess." If pressed a little harder, he might say, passes, the impressions of what we learn just get weaker and finally fade "Well, as time away.
If there is any truth at all in this notion, it cannot be the whole truth. Countless experiments have now demonstrated that it is not just the passage that determines how much we forget, but of time it is what happens during that time. What we do in between the time that we learn something and the time that we attempt to remember it influences how we will remember it. This can be demonstrated in experiments to be described in the following paragraph.
Memory after sleeping and waking.
Perhaps the most striking demonstration comes from a famous experiment in which the ability to remember after a period of sleep was compared with the ability to remember after an equal period of waking.