Paul Martin

COUNTING SHEEP

The science and pleasures of sleep and dreams

In spite of a great deal of research, there is still much that is unknown about sleep. Indeed, there is no agreement about the most basic question of all: what is the purpose of sleep? In fact, there are really two separate questions here, namely what is the purpose of deep (NREM) sleep and what is that of dreaming (REM) sleep, because these are quite different from each other. The popular names for these sleep phases are somewhat misleading, because dreaming occurs in both of them though predominantly in REM sleep. Both forms of sleep are surprisingly widespread across a vast range of organisms. All mammals, birds, reptiles, fish, and even insects that have been investigated appear to sleep, though I find it difficult to understand how we can be sure that when insects are immobile they are really sleeping in the mammalian sense.

A major theme of the book, which is treated at length in the first section and recurs frequently throughout, is Martin's view that most of us don't get enough sleep. Modern life, he believes, renders us liable to chronic sleep deprivation, and this is likely to affect our health and also impair our functioning when awake. The implications of this for drivers, pilots, doctors, and politicians are dwelt on somewhat alarmingly. There seems to be a widely held view that time spent sleeping is time wasted, but Martin will have none of it.

Other sections consider the physiological mechanisms of sleep and dreaming, the significance of dreams, the evolutionary origins of sleep, and the pathology of sleep; the final section strikes a lyrical note as it looks at the pleasures of sleep.

One of the more bizarre features of REM sleep is the phenomenon of nocturnal penile erections in males and similar physiological effects in females. For reasons of prudery or embarrassment they have been studied scientifically to only a limited extent. Since they occur during REM sleep, when most of our dreaming goes on, this might seem to support Freud's view of dreaming as predominantly concerned with repressed sexual desire, but the phenomenon is found in all mammals, not just in humans, and there seems to be no connection between nocturnal erections and sex or erotic dreams.

There is little agreement among scientists about the significance, if any, of dreams, though one popular idea is that they may be concerned with the processing and consolidation of memory. Martin does not accept Freudian or Jungian theories about the symbolic nature of dreaming, but he does allow that some dreams, at least, may provide insights for the dreamer and he thinks it is worth while learning to take notice of our dreams. He also has a chapter on the interesting phenomenon of lucid dreams, in which the dreamer realizes that he or she is dreaming and can guide the development of the dream to some extent.

As one would expect from the title, Martin provides some advice for insomniacs, though here he has little to offer that is new. He repeats the oft-quoted advice to avoid reading in bed, though I think that this is very much a question of what you are used to; I find that reading is one of the best methods of getting to sleep although admittedly the book has to be appropriate and not too exciting.

Martin presents a good popular science account of what is known, and unknown, about sleep. His writing is lively, sometimes excessively so; occasionally his style is rather too jokey for my taste and he appears to contradict himself once or twice. His sources are extensively cited in chapter notes.

15 September 2003