Psychologists have shown that a short nap lasting about an hour can significantly improve memory performance. The study involved examination of memory recall in 41 participants. The volunteers had to learn single words and word pairs. Once the learning phase was over, the participants were tested to determine how much information they could remember. About half of the participants were then allowed to sleep, while the others watched a DVD. After that, the participants were re-tested and those who had taken a nap were shown to have retained substantially more word pairs in memory than the participants in the control group who had watched a DVD.