Struggling with four across and eight down on your crossword? Then take a nap, a study suggests.
Scientists have discovered that getting forty winks improves your memory and helps you make links between loosely related facts.
Feeling refreshed after a full night's rest is also a great aid to "prospective memory" - being able to remember to do something in the future.
Researchers say the findings, published in the journal Psychological Science, help our understanding of the role sleep plays in brain processing as well as memory.
Professor Dr Mark McDaniel, a psychologist at Washington University in St Louis in America, said: "We found that sleep benefits prospective memory by strengthening the weak associations in the brain, and that hasn't been shown before."
The study found that sleep specifically helped us take advantage of what he calls "weak" memory cues, rather than "strong" ones.
The scientists tested 24 university students, asking them to perform different word games on a computer.
Some students were prepared for the test one evening and did it the following morning, while others did the test during the evening, after being prepared earlier that day.
The students who slept in between preparing and taking the test performed very strongly in the prospective memory test.
The researchers believe that the prospective memory process happens during 'slow wave' sleep – an early pattern in the sleep cycle — involving communication between two areas of the brain – the hippocampus and the cortical regions.
The hippocampus is very important in memory formation and reactivation and the cortical regions are keys to storing memories.
Michael Scullin, junior researcher, said: "We think that during slow wave sleep the hippocampus is reactivating these recently learned memories, taking them up and placing them in long-term storage regions in the brain.
"The physiology of slow wave sleep seems very conducive to this kind of memory strengthening."
Telegraph Media Group Limited