7. We all know that the normal human daily cycle of activity is of some
7-8 hours' sleep alternation with some 16-17 hour's wakefulness and that,
broadly speaking, the sleep normally coincides with the hours of darkness.
Our present concern is with how easily and to what extent this cycle can
be modified.
The question is no mere academic one. The ease, for example, with which
people can change from working in the day to working at night is a
question of growing importance in industry where automation calls for
round-the-clock working of machines. It normally, takes from five days to
one week for a person to adapt to a reversed routine of sleep and
wakefulness, sleeping during the day and working at night. Unfortunately,
it is often the case in industry that shifts are changed every week; a
person may work from 12 midnight to 8 a.m. one week, 8 a.m. to 4 p.m. the
next, and 4 p.m. to 12 midnight the third and so on. This means that no
sooner has he got used to one routine than he has to change to another, so
that much of his time is spent neither working nor sleeping very
efficiently.
The only real solution appears to be to hand over the night shift to a
number of permanent night workers. An interesting study of the domestic
life and health of night-shifty workers was carried out by Brown in 1957.
She found a high incidence of disturbed sleep and other disorders among
those on alternating day and night shifts, but no abnormal occurrence of
these phenomena among those on permanent night work.
This latter system then appears to be the best long-term policy, but
meanwhile something may be done to relieve the strains of alternate day
and night work by selecting those people who can adapt most quickly to the
changes of routine. One way of knowing when a person has adapted is by
measuring his body temperature. People engaged in normal daytime work will
have a high temperature during the hours of wakefulness and a low one at
night; when they change to night work the pattern will only gradually go
back match the new routine and the speed with which it does so parallels,
broadly speaking, the adaptation of the body as a whole, particularly in
terms of performance. Therefore, by taking body temperature at intervals
of two hours throughout the period of wakefulness it can be seen how
quickly a person can adapt to a reversed routine, and this could be used
as a basis for selection. So far, however, such a form of selection does
not seem to have been applied in practice.
1). Why is the question of "how easily people can get used to working at
night" not a mere academic question?
A. Because few people like to reverse the cycle of sleep and wakefulness.
B. Because sleep normally coincides with the hours of darkness.
C. Because people are required to work at night in some fields of
industry.
D. Because shift work in industry requires people to change their
sleeping habits.
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