Sleep that knits up the ravell'd sleave of care; The death of each day's life; sore labour's bath; Balm of hurt minds; great nature's second course; Chief nourisher in life's feast Do you get the impression that Shakespeare en-joyed a bit of shut-eye? If current research is on the right tracks, it's not surprising. Sleep, practically ignored by scientists for centuries, is suddenly hitting the headlines in neuroscience - and since it appears to be the key to both memory and creativity, it's of great interest to teachers too. In fact, Shakespeare's genius may simply be that he knew when to take a nap.
All teachers know lack of sleep has a bad effect on pupils' performance.
Children who haven't had enough sleep don't slow down as adults do; instead they display, in the words of one research project, "increased activity levels, aggression, impulsivity, and acting out, as well as poor concentration, inattention and moodiness". Sleepy children - and classrooms these days seem full of them - are in no fit state to sit down and learn anything.
However, it's now clear that lack of sleep also inhibits children's learning after the event. Neuroscientists have discovered that skills, facts and ideas acquired during the day are transferred into long-term memory during sleep. Scientists can see this on MRI pictures (magnetic resonance images of the brain at work) - when someone returns to a new skill or task after a night's sleep, different places light up in the brain from the places that lit up when the learning first happened.
Presumably, during sleeping time, while things are relatively quiet because no new input is being received, the brain is free to reorganise and tidy information - transferring new stuff into long-term memory and pruning out what's no longer required.
Different sorts of learning seem to be dealt with during different sorts of sleep. REM sleep (see box) is involved in the learning of practical tasks, such as how to ride a bicycle or write with a pencil, known by neuroscientists as "procedural tasks".
Dr Jan Born, a sleep researcher at Luebeck university in Germany, explained procedural learning thus: "To ride a bike, you just have to practise till it clicks. You don't need to concentrate intellectually, and you aren't particularly aware of what you've learned. You learn by trial and error, and lots of practice."
Primary children, of course, do a great deal of procedural learning - the younger the pupils, the more practical and practice-based their learning is.
During REM sleep the brain seems to rehearse new experiences from earlier in the day (experiments have shown patterns of activity in the brain during REM sleep precisely matching those displayed when people were actually practising the task). The next day, when a procedural learner repeats the task, it's easier. "These procedures are learned in chunks," says Jan Born.
"REM sleep appears to strengthen the processes leading to better chunking.
After REM sleep, when you practise again, the chunks can get bigger. The gain in this sort of learning is greater when there is lots of REM sleep."
To be effective, the REM sleep must occur within at least 24 hours of the learning; otherwise it doesn't improve performance at all.
Slow-wave sleep, on the other hand, seems to be important for learning facts or ideas - what the neuroscientists call "declarative memory". These are academic learning tasks involving concentration and conscious awareness of what's being learned - more common towards the top of the primary school.
During slow-wave sleep, the brain again appears to replay the information studied during the day, rather like an offline computer reactivating and replaying data. In the process it transfers the new learning from the hippocampus to the neocortex of the brain - that is, from an intermediate buffer zone into long-term memory. It is therefore very important to "sleep on it" when you've studied something, as even small reductions in slow-wave sleep have been linked to a decrease in memory function.
A recent study by Jan Born also suggests that the closer the learning is to the sleep, the greater the benefit - so a student who revises in late afternoon or evening is likely to retain more than one who works in the morning. If this is so, it has profound implications for education.
Teachers tend to believe children learn better in the morning when they're fresh. If Born is right, children may learn better then, but may not retain the information as well as they would if they studied in the afternoon.
Perhaps we should review the school day? At the least, we could ensure revision of new or important material in the afternoon.
But Born's most recent, and potentially exciting, discovery is that "sleeping on it" is also involved in creative thinking and problem-solving.
In an experiment that's been widely-praised by the international sleep-research fraternity, he gave some of his students a repetitive number task containing a hidden short cut. None of the students noticed this short cut while first practising the task, nor on returning to it after eight hours awake. But those who repeated the task after eight hours' sleep often spotted the short cut very quickly.
Born suspects that, when we return to a problem after sleeping on it, the fact that information has started transferring from one part of the brain to another renders us more able to make problem-solving leaps.
"What may be happening is that, due to this reorganisation, after sleep you get a slightly different perspective. So you now view the information from two perspectives, which means you could make a problem-solving leap." He points out that this leap doesn't typically come immediately after sleep - it comes when you start repeating the task.
It may, of course, be luck whether you hit a useful insight - presumably you could just as easily get a new perspective that makes you misunderstand. But why is it that some people, like Shakespeare, could score a million insights a day, while the rest of us only hit one once in a while? As Jan Born says: "The great question for researchers now is - how exactly are memories reorganised during sleep?" If he and his colleagues can answer that, the potential for education is huge.
In the meantime, this research clearly backs up the gut feelings of teachers across the globe that children need a decent night's sleep to flourish in the classroom. Sadly, the evidence is that they're actually sleeping less than ever: research suggests that, on the whole, children get about one and a half to two hours less sleep a night than they need.
There are all sorts of reasons. As one American research team summarised:
"The desire of working parents to spend evenings with their children and still bring them to day care or school early in the morning may infringe on sleep time. Homework, computer games, television, sports, lessons, social commitments and after-school jobs may all conspire to leave little time for sleep."
Teaching organisations ought to be screaming about this. If society wants teachers to raise a generation of little Shakespeares and Einsteins, they need to ensure children arrive at school in a fit state to learn. A good night's sleep is essential (decent diet, adequate exercise, parental time and interest, and no TV in children's bedrooms would be helpful too).
At present, too many children are languishing in classrooms, quite unable to knit up the ravelled sleeves of their chaotic lives, let alone learn anything.