The most natural time to take a nap, based on our circadian rhythms, is in the afternoon sometime between 2 and 4pm. The ideal time to snooze is when a nap would contain a good balance of slow wave and REM sleep. This balance typically occurs 6 to 8 hours after waking.

The best time to nap

The best way to nap also depends on what kind of effects you’re looking for:<ul><li>If you’re looking for a restorative nap, you should sleep later in the day when you have an increased amount of slow wave sleep.</li><li>If you’re looking for a nap that might aid your creativity and problem solving, you should sleep earlier in the day when you experience more REM.</li></ul>

Timing is everything

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Growing up, sleep was considered paramount in my family home. My siblings and I didn't have many house rules - bedtimes were flexible, we had free reign over microwaved TV dinners (this was the 1980s), and video games. But one thing was always crystal clear: we couldn't disturb an adult, or another kid, who was taking a nap.
As I got older, I was in for a rude awakening. Apparently, society looks down upon napping in the adult working world. But evidence is growing that napping can produce cognitive benefits from increased alertness to improved motor skills, perception and memory consolidation. So how do you get the best from a brief bit of shuteye?
In a <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0108100">study published last year</a>, researchers found that both nocturnal and daytime sleeping improved memory consolidation for unrelated word pairs - like 'pepper' and 'elbow' - suggesting it can help if you're trying to learn tricky-to-remember concepts. <a href="http://en.cnki.com.cn/Article_en/CJFDTOTAL-SQSZ201303030.htm">Another study</a>, conducted at the Beijing University of Technology, examined the effect of napping on athletes after training. It found that naps could improve brain function and visual systems, and promote physical and mental recovery - a result that is in line with earlier research demonstrating that <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000341">napping can facilitate motor memory consolidation</a>.
In a study published in 2008, the University of California's <a href="https://www.youtube.com/watch?v=MklZJprP5F0">Sara Mednick</a> - author of <a href="http://www.saramednick.com/">Take a Nap! Change Your Life</a> - and her colleagues compared the benefits of 200mg of caffeine ( <a href="http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/in-depth/caffeine/art-20049372">about the amount in a cup of coffee</a>) with a 60 to 90 minute daytime nap on various memory tasks. They found that a <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2603066/">nap generally improved memory performance, while caffeine either didn't affect - or worsened - performance</a>. The researchers suggest that caffeine blocks consolidation of new material into long-term memory by increasing levels of a neurotransmitter called acetylcholine in the hippocampus (the same neurotransmitter that naturally decreases during slow wave sleep).
The promised benefits of sleep have even persuaded a few firms to allow their employees to nap at work. Earlier this year, software company <a href="http://www.hubspot.com/">HubSpot</a> designed a napping room in its Massachusetts office that features a hammock and dim lighting. Employees are free to book the space without limitations.
According to HubSpot's Alison Elworthy, the policy is a huge success, especially helpful for new parents who are making up for disrupted sleep at night, or employees recovering from jetlag. "People are really excited to use it and haven't abused the policy at all," she says.
Other firms have had less success. Earlier this year, BBC Capital reported that <a href="http://www.bbc.com/capital/story/20140409-nap-rooms-gone-bad">napping policies led to slacking off and procrastination</a> at some companies, and a 30% drop in productivity at one Toronto-based tech start-up.
Even so, Mednick claims that about 40% of the population are habitual nappers - meaning they feel the need for, and benefit from, a regular afternoon snooze. So if you're a natural napper (and I am), what is the most effective way to nap?
The best way to nap According to researchers, the most natural time to take a nap, based on our circadian rhythms, is in the afternoon sometime between 2 and 4pm. Mednick even <a href="http://saramednick.com/htmls/book/napwheel.htm">designed a napping wheel</a> that pinpoints the ideal time to snooze, when a nap would contain a good balanced of slow wave and REM sleep. This balance typically occurs six to eight hours after waking.
But the best way to nap also depends on what kind of effects you're looking for. In a 2009 study, Mednick and her colleagues compared the effects of REM sleep, non-REM sleep, and quiet rest (while awake) on creative problem-solving. On the morning of the test, students were given a task in which they had to come up with a word that is associated with three apparently unrelated words - for instance 'falling', 'actor' and 'dust' can all be associated with the word 'star'. Early in the afternoon, the students either took an REM nap, a non-REM nap or spent time resting while awake. When they returned in the evening to repeat versions of the morning's test, the students who had taken the REM naps performed the best. In other words, it seems that <a href="http://www.pnas.org/content/106/25/10130.full">REM can enhance creative problem solving</a>.
"So if you're looking for a restorative nap, you should sleep later in the day when you have an increased amount of slow wave sleep," says Mednick, "And if you're looking for a nap that might aid your creativity, you should sleep earlier in the day when you experience more REM."
But getting REM sleep also means having to sleep for longer - about 60-90 minutes - because it is the last stage of the sleep cycle. Short naps can have benefits too, though.
A study in Australia found that a 10-minute afternoon nap was enough to <a href="http://www.journalsleep.org/ViewAbstract.aspx?pid=26564">help participants recuperate from a night of restricted sleep</a>. Participants felt less sleepy, more vigorous and showed improved cognitive performance for as long as 155 minutes following the nap. Though 20 and 30-minute naps also showed benefits, the cognitive improvements took longer to set in, presumably because participants needed to recover from the sleep inertia caused by the longer naps.
This ties in with research conducted by <a href="http://www2.hull.ac.uk/science/psychology/ourstaff/academics/johngroeger.aspx">John Groeger</a>, a professor of psychology at the University of Hull in the UK, which indicates that <a href="http://www.ncbi.nlm.nih.gov/pubmed/21463024">nappers should avoid complicated, higher-level executive tasks right after waking</a>. "When you wake you can do simple things pretty well," he said, "but your brain needs an hour or two to come fully back online."
Timing is everything Clearly, then, getting the timing of a nap right is key - which is something that <a href="http://www.hindawi.com/journals/isrn/2012/768794/">new smartphone apps and even intelligent sleep masks</a> are trying to capitalise on. <a href="https://neuroon.com/">NeuroOn</a>, a smart sleep mask that tracks brain waves and eye movements to wake you at the optimum time, raised four times its target in a <a href="https://www.kickstarter.com/projects/intelclinic/neuroon-worlds-first-sleep-mask-for-polyphasic-sle">Kickstarter</a> campaign in January, and is due to be released next year. It won't be the first smart sleep mask to reach the market. A similar device called Zeo briefly hit shelves in the US before <a href="http://mobihealthnews.com/20772/exclusive-sleep-coach-company-zeo-is-shutting-down/">the company shuttered last year</a>.
In a recent study, <a href="http://www.researchgate.net/profile/Nicola_Cellini">Nicola Cellini</a>, a researcher at the University of Padova, and his colleagues examined how Zeo compared to the " <a href="http://www.mayoclinic.org/tests-procedures/polysomnography/basics/definition/prc-20013229">polysomnography</a>" systems found in sleep labs in its ability to monitor sleep phases. Maybe unsurprisingly, they found that <a href="http://www.tandfonline.com/doi/abs/10.1080/15402002.2013.845782#.VGtmq_SUfmU">the Zeo performed relatively poorly</a> compared with the lab equipment - and certainly not to the standards required for sleep researchers.
Despite the results of the study, though, Cellini believes that it's only a matter of time before a personal mask that can accurately monitor a person's sleep comes to market. In fact, there is already some evidence showing that something as simple as two electrodes on the forehead can <a href="http://onlinelibrary.wiley.com/doi/10.1111/jsr.12105/abstract">accurately track sleep</a>.
All of this advice about enhancing your napping should come with caveats, however. For example, Elizabeth McDevitt at the Sleep and Cognition Lab at the University of California, Riverside is studying whether non-natural nappers who are trained to nap regularly experience cognitive improvements. Though the study is not yet published, she says that so far, it seems that non-natural nappers don't experience any gains. This means that if you don't feel the need to nap, forcing yourself won't help.
And Cellini and others are quick to reject the notion of <a href="http://www.polyphasicsociety.com/polyphasic-sleep/overviews/">polyphasic</a> sleep - a strategy in which people sleep for short periods throughout the day in order to spend less time sleeping overall. "No matter how you design it, napping is never going to be as good as getting a full night of sleep," he says.
It seems that to nap properly, you have to ask a professional how it's done. 
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Growing up, sleep was considered paramount in my family home. My siblings and I didn't have many house rules - bedtimes were flexible, we had free reign over microwaved TV dinners (this was the 1980s), and video games. But one thing was always crystal clear: we couldn't disturb an adult, or another kid, who was taking a nap.

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