(英会話リスニングスクリプト)
Robert Provine of the University of Maryland
says that people are not the only creatures who laugh.
Animals laugh too, especially monkeys and
their laughter sounds different from human laughter.
Professor Provine says human beings began
laughing before they could speak.
Laughing started about three million years
ago, when early humans first stood on two legs.
That made it possible for their lungs and
chests to make different sounds as well as breathe.
Professor Provine says people in all countries
begin laughing early in life.
Babies start laughing about four months
after they are born.
Many researchers believe laughter is a social
reaction that connects one person to another.
Laughter spreads among people.
Hearing someone else laugh can make you
laugh.
Some researchers say laughter may be a sign
that we trust those around us.
Professor Provine says people use laughter
as a way to ease another persons anger or make a threatening
situation safer.
Making a situation seem less serious reduces
any threat.
Yet one researcher says laughing is an aggressive
act.
He believes laughter began as a cry of victory
after a fight, and this feeling exists everytime someone
laughs.
Still others note that laughing is healthy.
It can relieve worry and tension.
Studies have found that laughing releases
natural painkillers in the body.
Laughing for several minutes increases the
heart rate, eases muscle tension and pumps carbon dioxide
out of the lungs.
It makes a person feel good.
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