What causes sleep? What causes us to withdraw partly our attention from
our environment? The answer: brain anaemia, is unsatisfactory for we may
ask in turn: what causes brain anaemia?
A study of brain anaemia leads one to conclude that it coincides with the
usual sleeping period and that it is produced by sleep instead of
producing sleep.
The large majority of laymen and scientists, however, give a much simpler
answer: we go to sleep because we are tired and need rest.
Even as sleep and death have been coupled in the literature of all
nations, fatigue and sleepiness, rest and sleep have come to be generally
considered as synonymous.
Fatigue, however, is as difficult to define scientifically as sleep.
Drawing a line between physical fatigue and mental fatigue does not
simplify the problem; on the contrary, it complicates it by positing it
wrongly.
We know that there is no purely physical fatigue. Fatigue is only caused
in a very restricted measure by the accumulation of "fatigue" products or
the depletion of repair stocks.
Under certain "mental" influences, our muscles can perform much more than
their usual "stint" without showing fatigue. Hypnotize a man and he will
do things he could not attempt in the waking state. He can lie rigid,
reposing on nothing but his neck and heels; he can even support in that
position the weight of a full-sized man. Men on the march can show
wonderful endurance provided their "spirits" are kept up by some form of
cheer, band music, etc. Ergograph observations show that signs of muscular
fatigue appear and disappear without any obvious "physical" reason.
Standardized motions which have been made almost automatic, tire us less
than conscious activity.
We shall not deny that in certain cases fatigue may appear purely
"physical." When a continued expenditure of energy, walking, carrying
heavy burdens, has induced muscular soreness, the organism must cease
exerting itself for a while and recuperate.
But relatively few people perform physical activities which actually wear
out the organism.
Even then, if that form of exhaustion was conducive to sleep, the more
complete the exhaustion was, the deeper the sleep should be.
Yet we know that people can be "too tired to sleep."
This is easily explained through a consideration of a phenomenon known as
the "second wind" and which, before Cannon's observations on the chemistry
of the emotions, was rather mysterious.
Athletes competing on the running track are often seen to falter and fall
back, apparently exhausted; after which, they suddenly seem to breathe
more freely, they overcome their limpness and start out on a fresh spurt
which may cause them to head off steadier runners.
What happens in such a case is this: great physical exertion causes a form
of asphyxiation. Asphyxiation and the concomitant fear, liberate adrenin
which restores the tone of tired muscles and also glycogen (sugar) which
supplies the body with new fuel.
If the exertion continues long enough to use up all these emergency
chemicals, the muscular relaxation necessary for sleep may be obtained.
Otherwise, the organism prepared for a struggle with reality, will not
lend itself to a flight from it. Although we are "worn out" we toss about
in our bed, try all possible sleeping positions and only sleep when the
energy which was supplied for a long struggle has been entirely burnt up.
The majority of people, after all, busy themselves with tasks which do not
really deplete their stores of energy, but which prove monotonous. That
monotony is then interpreted as fatigue.
In such cases, rest seems to be more easily attained through a change of
activity than through mere cessation of activity.
A business man has been closeted in his office attending to many tedious
details, reading letters and answering them, etc., and by five o'clock he
feels "tired." He will then go home, change his day suit for evening wear,
attend a dinner at which he will do perhaps much talking, then watch
actors for three hours and feel "rested."
Or at the end of a "heavy" week, he will gather up his golf outfit and
walk miles in the wake of a rubber ball. He returns to his work "rested,"
although he has only exchanged one form of activity for other forms of
activity. Of actual "rest" he has had none.
Children "tired" of sitting in a class room will romp wildly, shout at the
tops of their lungs, jostle and fight one another and return to meet their
teacher "rested."
Undirected activity in the young, pleasurable activity in the adult do not
seem to make rest necessary, and in fact are a form of "rest."
Egotistical gratification easily takes the place of rest. Heads of large
businesses have sometimes mentioned to me that they worked much harder
than some of their employés. Some of them kept on revolving commercial
schemes in their heads or attending business meetings long after their
office workers had left. "And yet," they added, "we are not complaining
about being tired." Nor were they as tired, after fifteen hours of "free
labor" as their employés were after six or eight hours of routine work
allowing them very little initiative and independence of action.
Edison works eighteen hours a day and only "rests" through sleep some four
hours out of the twenty four. I wager that if he were put at work in his
own plant, under the direction of a foreman, performing regular,
monotonous tasks, he would break down under the strain of such long hours
and would have to "rest" twice as much as he does now. His work satisfies
him, and every new detail he perfects, every novelty he initiates,
vouchsafes him a powerful ego gratification.
Napoleon, too, could perform incredible feats of muscular activity and
endurance after which four hours' sleep were sufficient to rest him. His
life was for many years a continuous round of ego gratifications, won at
the cost of great exertions, it is true, but proclaiming to him and the
world his almost unrestricted power and luck.
One is forced to the conclusion that a desire for rest is a desire, not
for decreased activity but for increased activity.
I shall make this point clear through a simile. The manufacturer who
"attends to business" must, in order to succeed, "concentrate" on a few
subjects and exclude all others from his mind. He may for a few hours
think of nothing but, let us say, a certain grade of woollens, certain
machinery, a certain customer and perhaps a certain engineer and some
financial problem connected with those four thoughts. He must therefore
exclude from his mind at the time, thoughts of playing golf, buying new
clothes, going to the theatre, renting an apartment, repairing his motor
car, thoughts of meals, women, card playing, and many other thoughts which
are clamouring for admission to consciousness because they all represent
human cravings.
In his relaxed moments he will let all those other thoughts come to the
surface. Which means that, what tired him, was the fact that he had to
keep all those subjects down and allow only the other four to rise to
consciousness.
Mental rest consists in admitting ideas pell mell into consciousness
without exercising any censorship on them. It consists in passing from a
reduced but directed mental activity to an increased but undirected mental
activity.
In other words, rest is the free, normal, unimpeded functioning of the
vagotonic nerves which upbuild the body and assure the continuance of the
race. Ego and sex activities, mental and physical, are constantly
struggling for admission to consciousness and for their gratification.
They are held down, however, by the sympathetic nerves which play the part
of a safety device, moderating or inhibiting the vagotonic activities
whenever the latter might endanger the personality.
Physical and mental rest, however, being easily attained through a change
of activities, cannot be entirely synonymous with sleep. Sleep takes place
mainly while we are resting, although we know of cases when sleep sets in
regardless of continued muscular activity, but sleep is not exactly
"rest." We do not sleep because we need rest. In many cases we can or
could rest very well, although in such cases sleep is an impossibility.
What then induces sleep? The certainty that we can for a time relax our
watch on our environment; a feeling of perfect safety; the conscious or
unconscious knowledge that no danger threatens us.
Our receptive contact with reality is attained through the action of our
vagotonic nerves which, as stated before, upbuild the body and assure the
continuance of the race. Our defensive contact, on the other hand is
attained through our sympathetic nerves which interrupt all the activities
which are not necessary for fight or flight. As long as some stimulus is
interpreted by those nerves as indicating a possible danger, we cannot
sleep, although we may, under the influence of terrifying fear, fall into
unconsciousness.
A light flashed on our closed lids at night causes us to wake up because
sympathetic activities bid us to prepare for an emergency. A light burning
evenly in our bedroom and not too bright to cause physical pain, will, on
the other hand, allow us to sleep soundly because the constant character
of the stimulus does not cause us to expect any danger therefrom.
A mouse rustling a bit of paper will wake us up, but trains passing in
front of our window at regular intervals, or the constant rumble of a
neighbouring power house will not prove a disturbance as soon as our
nerves have learnt to interpret those stimuli as harmless.
Conversation with a dull, witless person, unlikely to best us in debate,
puts us to sleep. Argument with keen, sharp-minded people, who keep us on
the defensive, may lead to sleeplessness for the rest of the night. A dull
book in which nothing happens or is expected to happen, acts as a
soporific; we cannot close our eyes before we know the dénouement of a
thrilling piece of fiction.
In other words, monotony transforms itself into a symbol of safety. Safety
does not require the muscular tension, the blood stream speed which the
organism needs in order to cope with possible emergencies. We "let go" and
no longer pay any close attention to our environment. We sleep.