Our Rhythms Still Follow the African Sun
By Marcia J. Thompson and David H. Harsha
From: Psychology Today, January 1984
1.
By early afternoon, the hunt is over. A pride of lions, having eaten their
fill, gathers in the shade of a thorn tree. Other animals drowse, play or groom
each other quietly. They have behaved this way in the early afternoon for
millions of years, in a land where the heat of the sun rules all. Far from the
tropics, Scandinavian factory workers make more mistakes on the job, German
schoolchildren stumble over their arithmetic exercises and Greek merchants
close their shops. In offices everywhere, people have returned from lunch, but
alertness flags and daydreams intrude. Some people tell themselves that they
must have eaten too heavily, while others begin to doubt that the hasty
sandwich was enough and listen for the bell of the coffee cart. In truth, the
post-lunch dip has little to do with food and much to do with our tropical
heritage. We have all experienced this fading sensation an hour or too after the
traditional noon meal. Yet, by late afternoon, whether we’ve napped, drunk
coffee or just plugged along, alertness returns. We rally in time to wrap up our
tasks, clear our desks and head home.
2.
There is an obvious temptation to attribute the phenomenon to
biochemical effects of eating, hence the “post-lunch” tag often attributed to
circadian researcher M.J.F. Blake. But why is there no similar reaction after
breakfast or supper, which in many cases are much heavier meals? In an
unpublished study, Blake tested three groups of 12 subjects for efficiency in a
range of tasks – vigilance; card sorting; time estimation and others – five times
during the day. There were no significant differences between the group that
ate lunch at 10 a.m., the one that ate at noon and the one that ate at 2 p.m. Yet
all three groups experienced a mid-afternoon drop in efficiency. Many other,
more recent studies have documented the same pattern among people in varied
cultures and occupations all over the world.
3.
For years, another popular explanation for fluctuations in efficiency was
body temperature. As our temperature rises and falls, it was said, so does our
efficiency. But in fact, body temperature rises steadily through the morning,
reaching its high point in early or middle afternoon, just when our ability to do
all but the simplest tasks declines markedly, but efficiency rises again later in
the afternoon, as body temperature declines toward its low point at night when
we sleep.
4. If food isn’t the answer, or temperature, what does explain the post-lunch
dip and the other variations we experience daily? Nearly every process in our
bodies, from glandular secretions to our ability to memorize telephone
numbers, fluctuates in a predictable 24-hour cycle. Researchers have plotted
peaks and troughs of more than 100 physiological and performance variables,
each with its own natural period, which may be longer or shorter than 24 hours.
The periods are coaxed into synchrony by zeitgebers, or time cues, that mesh
them with our patterns of sleeping and waking.
5.
We believe that the explanation lies in the tropical environment in which
our species evolved. We have lived in temperate climates for less than a million
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years, and only in the last hundred thousand years or so have we wandered into
the sub-arctic latitudes. In evolutionary time, this was last week. Man is still
fundamentally a tropical creature. Warm-blooded tropical animals exhibit a bigeminous, or two-peaked, daily rhythm of activity, with the late-morning peak
more marked than the late-afternoon one. This rhythm, we suggest, stayed with
us after we left the African plains, and continues to thwart our efforts to live
and work as if the hours of the day were as identical as spark plugs off an
assembly line.
6.
Our primate relatives all observe a midday lull in activity. Generally,
monkeys and apes spend their mornings in active, noisy communal feeding.
During the hottest part of the day, roughly from one to three hours after noon,
activity subsides. This is not a mere rest period, but a time for a different sort of
activity. Older primates groom each other and their young, poking patiently
through each other’s fur rather than dozing; some use the time to build sleeping
nests for the night to come. Jane Goodall’s chimpanzees follow a similar
pattern, sleeping for half an hour and spending the rest of the lull sprawling idly
or grooming. Later in the afternoon, the animals resume active feeding until
sunset.
7. The periods of high collective activity can be considered the primates’
working times, when they fulfill the most basic function of feeding themselves.
By contrast, relaxed grooming and play may seem much less vital pursuits. But
these are highly social species. During grooming and play, they reinforce the
dominance and bonding relationships that establish social structure. Primates
seem to seize the time when lions or elephants drowse as an opportunity to
carry out activities which require less alertness but are just as necessary as
eating.
8. Among humans, we find a rich and varied array of daily activity. The most
striking difference from other animals, of course, is that fire and electricity
have stretched our day beyond the limits set by the sun enabling us to add a
new set of nighttime activities. These, too, show intriguing common threads
9.
Let us sketch a simplified, worldwide human day. In the morning, a
woman of the household arises and rekindles the fire, putting water on to boil.
This occurs, with technological variations, among the Mbuti pygmies, the Irish,
the Monguors and the Americans. Men and children often awaken a little later.
Morning ablutions and other preparations for the day accompany breakfast.
10. After the morning meal, adults engage in the most important work of the
day, work connected with the group's subsistence. The Shilluk and the Navajo
herd their livestock. The Mixtecs, the Rajputs, the Maltese, the Yucatec Maya
and the Koreans work their fields. Samoyed men hunt wild reindeer and Arctic
geese. Women may participate in this labor or do their own work, often in
cooperation with other females.
11. The midday meal may occur any time between 11 a.m. and 2 p.m. In
most societies, it is a family meal with the breadwinner returning from work.
Less often, the women and children eat at home while the men eat at work.
12. Then comes the afternoon lull. In nonindustrial cultures, this break is
nearly universal. People retreat from the heat of the sun in warm climates, often
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choosing sedentary individual or small-group pursuits such as repairing tools or
weaving mats, rather than those requiring large-group cooperation. Adults may
visit and chat, while children play. Despite a common tendency to speak
disparagingly of the "siesta”, naps are not the usual activity, even in the tropics.
13. In the late afternoon, people resume animated activity, at a pace slower
than the morning's. They continue until sunset, depending on the time of year
and how long it takes to travel between work and home.
14.
The end of the workday is a social time; some variant of the cocktail
hour occurs in many cultures. In Indian Latin America, women gather inside
each other's homes for novenas, while husbands outside discuss politics and
business. In Spain, older students crowd into bars to drink with their cronies
before going home. 1n rural Okinawa, people invite their neighbors in for tea
and sweets. Strong drink is often part of the ceremonial transition from work to
the dinner hour.
15. After dinner, early-rising groups usually end the day in sleep by 10 or 11
p.m. But the young, the strong, the enthusiastic (and even the early risers on
ceremonial occasions) may enter a late-night, optional phase reserved for
especially intense activities. Contacts are less likely to be business or political,
more likely to have emotional, erotic and sometimes hostile overtones.
16.
In American college fraternities and dormitories, this is the time when
revellers hear the call to "rally." On Broadway, composers of musicals insert
what they call an "11 o'clock song," a boisterous number designed to rouse a
fading audience and hold its attention through the last act. In modern Spain, the
10 p.m. to 11 p.m. dinner hour marks the distinction between the early-evening
round of theater and club activity (after which well-brought-up young people
should be home) and more intense social functions. A popular song of the
1960s, "Poco antes de que den las diez" ("A little before 10"), told of a young
girl who rushes from her lover's bed to get home in time for supper. The song
mocked the traditional belief that early evening is sexually safe while later
hours are dangerous... but it is the belief that counts.
17. We have found such daily transitions in societies from equatorial to polar
latitudes; among nomadic hunter-gatherers and workers in modern industrial
nations. No culture institutionalizes every phase, but when it doesn't vestiges
can often be found in casual behavior. This near-universality suggests that the
transitions have a biological base. We believe they do, but the basis is complex,
as the levels of hundreds of hormones, neurotransmitters and other body
chemicals rise and fall with their own circadian rhythms. Until we know much
more about the interactions of such substances, we may learn more by looking
carefully at cross-cultural patterns in daily activity.
18. Whether the human organism is examined from the cell out or from the
society in, it remains faithful to the rhythm of the tropical day that shaped its
activities until very recently. Our ancestors learned to avoid heat stress on their
uniquely complex nervous systems. While both prey and predators slept, they
did things they alone needed to do: manufacturing and caring for their tools,
making the fabrics that came to replace other primates' fur, refining the
symbolic connections that made them fully human.
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19.
In America today, most of us go through daily routines that are less
predictable than those of a peasant farmer, a fisherman or even a factory
worker. Tasks are often distributed haphazardly, on an as-needed basis
throughout the workday, which we divide symmetrically with three to four
hours before lunch and about four hours afterward. We assume that these hours
are functionally identical.
20. But if we keep the traditional lunch hour starting about noon, we cut out
the most productive part of the day, when our mental and motor aptitudes are at
their peak. It would be better to schedule lunch an hour or two later, in keeping
with the bigeminous patterns of cultures all over the world, as well as those of
nonhuman primates. This would place lunch at the beginning of 'the dip in
alertness, a time best suited for conversations, such as business lunches, and
still leave a concentrated work period at the end of the day.
21.
A business day restructured in this way would have important meetings
and other activities requiring cooperation scheduled for mid- to late-morning.
Mid-afternoon would be reserved for less demanding mental tasks; a time for
visits rather than meetings, for communication to strengthen ties rather than to
exchange vital information. The mid-afternoon is not a period during which
people deal well with the unexpected or the demanding task.
22. Later, when efficiency and energy were on the upswing, we would return
to vigorous activity, perhaps taking up a limited project that requires full
concentration. These valuable hours should hot be wasted in simply cleaning
up work begun earlier.
23. The content of our workdays has changed, but our tropical origins are
still with us. Though we drill for oil beneath the ice caps and walk on the
moon, though we shuffle our work routines to accommodate new production
quotas and overseas conference calls, we remain subject to the dictates of the
African sun.
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Questions should be answered in your own words, in English, unless
otherwise indicated.
Choose the best answer
1. What is the main idea in the first two paragraphs?
Lions display marked indications of declining activity in the early
afternoon.
b. It is natural for people who have had a solid meal to need a rest.
c. One should eat a hearty breakfast rather than a solid lunch.
d. All primates and men display a diminished capacity in the early afternoon.
Answer the questions below in English.
2. What particular fact, paragraph 3, would refute the thesis attributing
decreased activity to falling body temperatures?
Answer: _______________________________________________________
______________________________________________________________
_______________________________________________________________
3. In what climatic zone, paragraph 5, did the human species evolve?
Answer: _______________________________________________________
4.
When do warm-blooded creatures reach the peak of their daily rhythm of
activity?
Answer: _______________________________________________________
Complete the sentence below.
5. Paragraph 5 suggests that our unfailing decline in activity which occurs in the
early afternoon hours, is to be attributed to
______________________________________________________________
______________________________________________________________
Answer the question below in English.
6. How do primates, paragraph 6, usually spend the early afternoon hours?
Answer: _______________________________________________________
______________________________________________________________
Choose the best answer.
7. Paragraph 7 suggests that among monkeys and apes the gathering of food and
its consumption are not carried out
a. collectively.
b. regularly.
c. singly.
d. by all members of the community.
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Answer the question below in English.
8. Two elements, paragraph 8, have contributed to the lengthening of our day;
what are they?
a. ____________________ b. ______________________.
Choose the best answer.
9. The various human activities mentioned in paragraphs 9-17 inclusive are
described in this article in order to
a. show how human cultures vary.
b. emphasize the fact that some cultures attach greater importance to hard
work.
c. show how we might benefit from the experience of less sophisticated
societies.
d. demonstrate the fact that all human cultures - regardless of degree of
sophistication -- share common patterns of activity.
10. The claim, paragraph 17, that the pattern of human activity is attributable to
factors rooted in our evolutionary development will, for the time being, have
to rest upon a study of the various cultures because
a. the argument is essentially a cultural one.
b. they make for greater interest.
c. the available cultural evidence is still rather controversial.
d. biology has as yet not provided a clear answer on this issue.
Complete the sentence below.
11. Whether we study the human organism from tbe cell out or from the society
in, we reach essentially the same conclusion, in fact it means that both the
____________ evidence and the ___________________ evidence point to
the same conclusion.
Answer the questions below in English.
12. In paragraphs 20-21, the authors recommend a change in working hours in
our societies; what do they suggest?
Answer: ______________________________________________________
_____________________________________________________________
_____________________________________________________________
13.
Sum up the main idea of this article.
Answer: ______________________________________________________
_____________________________________________________________
_____________________________________________________________