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CAUGHT napping? Clever you! Once a sign of laziness, it鈥檚 now clear that taking 40 winks is a great way to improve your performance.

A 鈥渘ano-nap鈥�, lasting just 10 minutes, can boost alertness, concentration and attention for as much as 4 hours. Take 20 minutes and you increase your powers of memory and recall, too. Either way, you are unlikely to enter the deeper stages of sleep, so will avoid the phenomenon known as sleep inertia, the groggy feeling that can occur when waking from deep sleep. On the flip side, you won鈥檛 get the benefits of deep sleep. However, light sleep turns out to be more important than we thought.

鈥淭here are wonderful little champagne cork bursts of electrical activity that happen during light sleep, called sleep spindles, and the field of sleep research is rapidly seeing that they have learning and memory benefits,鈥� says of the University of California, Berkeley.

Still, deep sleep provides the biggest boost to learning. If that鈥檚 your aim, opt for a nap of between 60 and 90 minutes, says Walker. His research shows this aids learning by shifting memories from short-term storage in the brain鈥檚 hippocampi to lockdown in the prefrontal cortex 鈥� a bit like clearing space on a USB memory stick, Walker says. As well as helping you to retain factual information, longer naps can increase motor memory, which is useful for training skills such as sport or playing a musical instrument.

A longer nap could also improve your equanimity. If you are feeling emotional, try snoozing for 45 minutes or more. This should take you through a stage of REM sleep, and brain scans of people following a REM sleep nap showed .

Bear in mind, though, the time of day you nap may affect the type of sleep you get. During the night, each 90-minute sleep cycle includes a bout of non-REM sleep followed by REM sleep (see diagram). However, deep non-REM sleep tends to dominate in the first half of the night, with the balance then shifting to REM sleep. A morning nap is much more likely to contain REM sleep, says Walker, 鈥渂ecause your brain still has a preferential hunger for it鈥�. In the afternoon and evening that changes. So, morning naps are likely to contain more emotionally calming dream sleep and afternoon naps more restorative and memory-boosting deep sleep. Still, Walker warns against trying to hack your sleep to pick the benefits, because your brain may just take the kind of sleep it needs.

Besides, for all of us, the urge to nap is strongest at one particular time of day: after lunch. Don鈥檛 blame what you鈥檝e eaten but your circadian rhythms (see diagram 鈥�The drive to sleep鈥�). 鈥淓veryone has this little pre-programmed drop in our alertness, as if we want to go to sleep,鈥� Walker says. Succumb, and it could benefit your body as well as your mind. Greek men who did away with a siesta, for example, and increased rates of cancer. Walker puts this down to a loss of deep sleep. 鈥淒eep sleep lowers your blood pressure and lowers the contracting speed of the heart, so that you wake up with a better managed cardiovascular system,鈥� he says.

If you鈥檙e tempted to nap, it鈥檚 easy. Find a warm, dim and quiet place to lie down (getting to sleep when you鈥檙e sitting ). And if you want to keep it short, simply drink a cup of coffee immediately beforehand 鈥� the caffeine kicks in after about 20 minutes, wiping away the sleep inertia and leaving you raring to go.

We answer all the questions keeping you up at night in 鈥淪leep: A user鈥檚 guide鈥�

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This article appeared in print under the headline 鈥淗ow can I nap like a pro?鈥�