Do we need to sleep as much as we do? This, and other provocative questions, are dealt with by Stanley Coren, a professor of psychology at the University of British Columbia, in his most recent book, Sleep Thieves.
The anecdotal evidence on the amount of sleep people need is mixed. Persons as varied as Leonardo Da Vinci, Thomas Edison, Ezra Pound, Winston Churchill, Salvador Dali, and Joseph Stalin are said to have survived and even thrived on very little sleep. Some of these alleged constitutional insomniacs expressed pride at their ability to evade sleep. As General Volkogonov's recent biography of Stalin points out, he delighted in conducting affairs of state well after midnight and was accustomed to summon his ministers at three or four in the morning without the slightest hesitation. Edison is often quoted as saying: "Most people overeat 100%, and oversleep 100%, because they like it. That extra 100% makes them unhealthy and inefficient. The person who sleeps eight or ten hours a night is never fully asleep and never fully awake-they only have different degrees of doze through the 24 hours."
It is common in the business and professional world for careerists to emphasize their dedication, competence, and professionalism by working extremely long hours and evading sleep. The proverbial "all-nighter" is a staple of university student lore. The argument that we could do with less sleep is attractive on the surface. Certainly, most North Americans eat somewhat too much, because eating is pleasurable and because human beings are genetically programmed to prepare their bodies for times of scarcity. It might be reasonable then to think likewise that humans, if left alone, sleep eight to ten hours a night because sleeping is pleasurable too, and because, at least, in ancient times, it was imprudent to move around at night when our ancestors were subject to attack by wild beasts with better night vision than our own.
The weakness with the argument that one can reduce one's sleep and have more hours of productive activity (a sleep diet, so to speak) starts to appear when we look more closely at the anecdotal evidence of heroic insomniacs. For example, there really is no evidence that Leonardo Da Vinci only slept four hours a night, as has been alleged. On the contrary, certain references to Da Vinci towards the end of his life explicitly state that he slept longer than most and spent a considerable time in bed. As for Stalin, he often stayed up almost all night but he made up for it by sleeping during the day. He was aware that the Soviet workers paid attention to how hard he worked-being "the man of steel"-and he carefully fostered the belief that he never slept. When he did sleep at night, he ordered that the lights in his office be kept burning at all times so that passers-by outside the Kremlin could see that Stalin never slept.
Professor Coren relates an interesting anecdote about Edison towards the end of his book:
"The automaker Henry Ford once made an unexpected visit to Edison's lab. One of the technicians stopped him from entering Edison's private office, noting that `Mr. Edison is taking a nap.' Ford thought this was a bit amusing and said, `I understood that Mr. Edison didn't sleep very much.' `Oh, that's true,' said the technician. `He doesn't sleep very much at all, he just naps a lot.' "
Similarly, and perhaps heartlessly, Nikola Tesla, the Croatian electrical engineer who invented the rotating magnetic field and developed alternating electric current systems, noted that Edison required only four hours of sleep at night, but also needed two or three hour naps during the day.
Sleep's importance is shown in the fact that almost all animals sleep. Every species of mammal that has ever been tested has shown a sleep pattern, including marine mammals. The difficulty of obtaining sleep for such animals is immense:
"Consider the Indus dolphin which gets its name because it lives off Pakistan in the Arabian Sea near the muddy delta formed by the Indus River, which flows from the Himalayan Mountains. Over its entire life this dolphin never stops swimming. If it did, it would risk serious injury from the extremely dangerous currents in the region and the vast quantities of debris that are carried down the river and into the sea, especially during the monsoon season. Sleep in the form we have come to expect it (where an animal stops to rest in one position) is not found. However, despite the dangers associated with sleep in this environment, sleep has not actually disappeared. When electrical recordings of the brain of the Indus dolphin were taken, it was found that the animal actually sleeps around seven hours a day. The trick is that the dolphin does not sleep in a continuous seven-hour block of time but instead takes very brief naps, with the longest around 60 seconds in duration and the shortest as brief as four seconds. ... The fact that sleep has remained, even if it has to be taken in tiny naps, suggests that it must still perform some important function for the animal."
Professor Coren also writes about the danger sleep poses to a giraffe. Unlike some grazing animals, such as the horse, the giraffe cannot lock its legs and sleep standing up. It must lie down to sleep. When it awakes, standing up often takes as long as a full minute. If roused by attack, the giraffe cannot react immediately. While it is getting to its feet, the animal is completely unprotected and can be attacked by predators. As Coren says, "To place the giraffe in such a position of vulnerability each day, sleep must be very important indeed".
But what is the function of sleep? This tantalizing question is still a mystery. At most, there are hints that sleep is needed for the immune system but why is unknown. Francis Crick suggests that sleep, and dreams in particular, involve an unlearning process, by which the brain discards irrelevant material; this thesis is speculative at best and without evidence to support it. Our understanding of why we sleep is little, if at all, clearer than the view of Empedocles, the pre-Socratic speculator, who explained sleep as the cooling of the blood caused by the separation of fire from the other three elements.
The Freudian view has been that dream sleep is required to work out the anxieties of life. This seems to have been undermined by the discovery that all mammals undergo rapid eye movement during sleep, from which it appears-according to our current knowledge-that all mammals dream. Similarly, unborn infants in the womb spend a considerable amount of time apparently dreaming in rapid eye movement sleep. Unborn children and animals are hardly likely to working out their unresolved daily emotional traumas. Of course, it may be that unborn children are exercising their dreaming abilities, and we have no reason to think that animals do not have emotional and psychological problems. Still, dreaming fetuses and cows would pose some challenge to the Freudian interpretation of dreams.
But there is no doubt that a lack of sleep leads first to failures of judgement, then to hallucinations and psychotic episodes, and finally to death. The advantage of sleep deprivation as a kind of torture is that it is afterwards virtually undetectable. When rats, for example, are deprived of sleep for more than about two weeks, they die, but post-mortem examinations do not reveal any obvious physical or biochemical condition leading to death. Indeed, immediately before death, the only obvious physical problem is a lack of bodily temperature control. Once this stage of sleep deprivation is reached, the deprived creature dies, even if allowed immediately to sleep.
So the use of sleep deprivation as part of torture is very common; Amnesty International reports that up to 54 percent of torture victims interviewed are deprived of sleep for 24 hours or more during torture. Professor Coren notes that "continued disruption or deprivation of sleep has been called one of the most potent means of `softening up' prisoners. It is often used quite deliberately to obtain false confessions and, if it is continued long enough, the torture victims often come to believe that the false statements they make are actually true." Recently in Toronto there was a false confession to a series of rapes made by someone arrested by the police. He later alleged that he had made the false confession only after being kept awake for a long time. Interestingly, if it were not for unequivocal genetic testing demonstrating that the man who confessed could not have been the criminal, his confession would certainly have led to an extended prosecution and most likely to a conviction.
Professor Coren expresses concern that modern society is, generally, sleep-deprived and that this lack of adequate sleep leads to errors of judgement every day, causing a vast number of unnecessary accidents and death. The evidence he marshals for this view, particularly the evidence based on the use of daylight savings time in Canada, is striking. Coren thinks the problem of lack of sleep dates from the 1913 development of the modern tungsten filament light bulb; this is questionable. Certainly city-dwellers did not go to sleep at sunset in late Victorian England. Indeed, the sparkling social life of the 1890s depended in large part on the powerful illumination of gaslight. Napoleon was supposed to have slept so briefly as to weaken his judgement. And earlier, Jewish literature is full of references to scholars studying through the night. (For example, the Shulhan Arukh notes that it is customary to stay awake the whole of the night before Hoshana Rabbah, studying.)
All that said, it is clear that in North America, the amount of sleep has fallen over the last few generations. In 1910 the average young adult in North America slept about nine hours a day. Today the corresponding figure is something less than seven-and-a-half hours. In the last twenty or thirty years, the disintegration of the traditional job market and the replacement of employees with fixed hours by "consultants" who are forced to work an endless number of hours have had an immediate and palpable effect on the way business and professional life is conducted. When the Perry Mason television series was made, Mason's twenty-four hour availability to clients and continual presence at his office at all hours of the day or night were either a joke or a testimony to his superhuman legal abilities and dedication. Today, very ordinary lawyers are available to their clients almost twenty-four hours a day, and twelve-hour days, six days a week, are the norm rather than the exception. Even the casual observer can see that this type of life is not healthy and affects the judgement of the sleepless. One might wonder whether the present, and widely bemoaned, lack of civility in public life is a result less of changes in the structure of society than of sleeplessness. A tired person is a testy person.
Professor Coren's book is remarkably readable and is a solid introduction to the present scientific understanding of sleep and its effects on North American society. He writes with verve and competence and has produced one of the most interesting and readable books of popular science I have read in a long time.

James Morton is a lawyer practising with Steinberg Morton Frymer in Toronto. He teaches at Osgoode Hall, serves on numerous legal and political committees, writes on various topics and is, as a direct and immediately foreseeable result, sleep-deprived.