Counting Sheep: The Science and Pleasures of Sleep and Dreams. Paul Martin

resemble places of entertainment rather than places of sleep. When given the opportunity, we sleep in at the weekends and feel only half awake when we do get up. On that long-awaited holiday we find the change of scenery (or is it the air?) makes us even sleepier. We are told that lying around and sleeping too much will only make us sleepier. But in truth we feel sleepy at weekends and on holidays not because we are sleeping too much, but because we have slept too little the rest of the time.

      A century ago the majority toiled long hours while the affluent few idled away their time. Today, however, the more conventionally successful you are, the less free time you will probably have. Having nothing to do is seen as a sign of worthlessness, while ceaseless activity signifies status and success. Supposedly unproductive activities are deprioritised or delegated. And according to prevailing cultural attitudes, sleeping is one of the least productive of all human activities – more worthwhile perhaps than sitting around picking your nose, but not much. In their ceaseless pursuit of work and pleasure the cash-rich buy time from others, hiring them to clean their houses, look after their children and cook their food. But one of the activities you simply cannot delegate to anyone else is sleeping.

      Evolution equipped humans, in common with all other animals, with biological mechanisms to make us sleep at roughly the same time every day. However, those mechanisms evolved to cope with a pre-industrial world that was vastly different from the one we now inhabit.

      Our daily cycles of sleep and activity are no longer driven by dawn and dusk, but by clocks, electric lighting and work schedules. Sleep has become increasingly devalued in the 24-hour society. Many regard sleep as wasted time and would prefer to sacrifice less of their busy lives to it. We live in a world where there are too many tired, sleep-deprived people. Think of those pinched, yawning faces you can see every day on the trains and in buses and in cars crawling through jams. They look as if they have been brainwashed, but they are just tired.

      We pay a steep price for neglecting sleep, in our ignorance and indifference. The scientific evidence tells us that far too many people in industrialised societies are chronically sleep-deprived, with damaging consequences for their mental and physical health, performance at work, quality of life and personal relationships. William Dement, a pioneering scientist in the field, believes that we now live in a ‘sleep-sick society’. Scientists have not yet reached a consensus about the precise extent of sleep deprivation in society, but they do all agree that sleepiness is a major cause of accidents and injuries. In fact, sleepiness is responsible for far more deaths on the roads than alcohol or drugs.

      Everyone has heard about the need for a balanced diet and physical exercise, even if many of us fail to follow the advice. But sleep is lost in a deep well of ignorance and apathy. Even the medical profession pays it scant regard. Sleep and its disorders barely feature in the teaching of medicine, and few physicians are fully equipped to deal with the sleep problems they regularly encounter. When researchers from Oxford University investigated British medical education in the late 1990s, they discovered that the average amount of time devoted to sleep and sleep disorders in undergraduate teaching was five minutes, rising to a princely peak of 15 minutes in preclinical training. Your doctor is therefore unlikely to be an expert on the subject.

      The general public and the medical profession are not the only ones to display a remarkable indifference to sleep. So too do most contemporary writers. Considering that sleep accounts for a third of human existence, it features remarkably rarely in novels, biographies, social histories or learned texts on neurobiology, psychology and medicine. And the few accounts that have made it into print are mostly concerned with what happens when it goes wrong. Insomnia and nightmares loom large in the tiny literature of sleep.

      Few biographies mention the sleep behaviour or dreams of their subjects. That part of their story is almost invariably missing, as if somehow we all cease to exist at night. And most of those scholarly books that set out to explain how the human mind works say little or nothing about what goes on during the several hours of every day when the mind is sleeping and dreaming. They are really just books about how the brain works when it is awake. Our neglect of sleep is underlined by its absence from our literature.

      Vladimir Nabokov once said that all the great writers have good eyes. What has happened to the eyes of writers as far as sleep and dreams are concerned? It was not always so. Older literature is distinctly richer in references to sleeping and dreaming, perhaps because darkness and sleep and dreams were much more prominent aspects of everyday life before the invention of the electric light bulb and the advent of the 24-hour society. Shakespeare’s works are thick with allusions to sleep and dreams, as are Dickens’s. We shall encounter some of them later. Meanwhile, to set the right tone, here is Sancho Panza’s eulogy to sleep from Don Quixote:

      God bless the inventor of sleep, the cloak that covers all man’s thoughts, the food that cures all hunger, the water that quenches all thirst, the fire that warms the cold, the cold that cools the heat; the common coin, in short, that can purchase all things, the balancing weight that levels the shepherd with the king and the simple with the wise.

The universal imperative

      Almost all other animals are observed to partake of sleep, aquatic, winged, and terrestrial creatures alike. For every kind of fish and the soft-shelled species have been seen sleeping, as has every other creature that has eyes.

      Aristotle (384–322 BC), On Sleep and Waking

      Sleep is a universal human characteristic, like eating and drinking. Absolutely everybody does it. Sleep occupies about one third of each human life, and up to two thirds of a baby’s time. (According to Groucho Marx, the proportion rises to three thirds if you live in Peoria.) It is a common bond that ties us all together. We have no choice: the longer we go without sleep, the stronger our desire for it grows. Tiredness, like hunger and thirst, will eventually force us to do the right thing whether we want to or not.

      The dreams that accompany sleep are equally ubiquitous features of human life, even if many of us retain little memory of them after we awake. Dreaming is a classless activity that unites monarchs and paupers, a thought that Charles Dickens mused upon in one of his essays:

      Here, for example, is her Majesty Queen Victoria in her palace, this present blessed night, and here is Winking Charley, a sturdy vagrant, in one of her Majesty’s jails … It is probable that we have all three committed murders and hidden bodies. It is pretty certain that we have all desperately wanted to cry out, and have had no voice; that we have all gone to the play and not been able to get in; that we have all dreamed much more of our youth than of our later lives.

      Sleep is not a specifically human trait, of course. On the contrary, it is a universal characteristic of complex living organisms, as Aristotle deduced more than 23 centuries ago. Sleep is observed in animals of every sort, including insects, molluscs, fish, amphibians, birds and mammals. Within the animal world, sleep does vary enormously in quantity, quality and timing, accounting for anything up to 80 per cent of some animals’ lifespans. But they all do it, one way or another. Some species, especially predators, spend more of their lives asleep than they do awake, a fact that TV documentaries and natural-history books seldom mention.

      How do we know that an animal is sleeping? It is hard enough sometimes to be sure that a human is asleep, let alone a fish or a fly. The ultimate indicator of whether an animal or person is asleep is the distinctive pattern of electrical activity in its brain. During deep sleep the billions of individual nerve cells in the brain synchronise their electrical activity to some extent, generating characteristic waves of tiny voltage changes that can be detected by electrodes placed on the scalp. We shall be exploring the nature and internal structure of sleep later. The easiest way to recognise sleep, however, is from overt behaviour.

      Sleep has several rather obvious distinguishing characteristics. A sleeping person or animal will generally remain in the same place for a prolonged period, perhaps several hours. There will be a certain amount of twitching, shifting of posture and fidgeting. Young animals will suckle while they sleep and ruminants will carry on chewing the cud. But sleepers normally do not get up and change their