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Why do people yawn ? No one seems to know the
exact ___1___.
Some people believe that we yawn ___2___
we do not have enough oxygen in our bodies. In ___3___
words, we yawn to breathe in ___4___
oxygen. People also believe that yawning is
associated ___5___
boredom. For example, ___6___
a monotonous and dull lesson, you may feel bored ___7___
tears. At that time, you are ___8___
to yawn very often.
Yawning can also ___9___
contagious. Have you ever had the ___10___
of a long wait at the doctor's clinic ? During the
wait, someone may ___11___
a long, tired yawn. When this ___12___,
other people in the room may start to yawn ___13___.
A psychologist, Dr Robert Provine, did some
studies ___14___
yawning. In one of ___15___
experiments, Dr Provine asked his subjects to record ___16___
the times of the day ___17___
they yawn. He discovered that yawning is ___18___
common during two times of the ___19___
- the hour before sleep ___20___
the hour after waking. He concluded that yawning is
related
___21___
stretching. People tend to yawn when they stretch ___22___.
Dr Provine also ___23___
several other interesting findings. ___24___
of these findings is that people who read about
yawning would start yawning. In fact, according to
him, people ___25___
think of yawning would start yawning.
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