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綜合寫(xiě)作

While scientists have been seriously observing behavior for well over a hundred years, the study of why animals play has only recently become a serious research topic. At least three different theories have been advanced to explain the phenomenon.

The first theory is called the surplus energy theory. This theory maintains that some animals, mammals for example, are so efficient at using energy that they often do not manage to spend all the energy they receive through food. They end up with unused, surplus energy that they cannot store. According to this theory, animals have to play to get rid of the surplus energy that they have not used.

A second theory is called the instinct-practice theory. It states that young animals play as part of their physical education. The physical actions that animals will need to use for survival are instinctual, that is, preprogrammed in their brains. The animals, however, have to train their bodies to be able to perform these actions. So this theory explains why the play of young animals centers on real-life tasks. For example, predatory animals those that hunt, kill, and consume other animals for food—have often been observed attacking and biting during play, which are precisely the skills they will need in order to hunt for food.

A third theory, called the social functions theory is that animals play to establish social relationships within their group. Basically, play gives animals a chance to bond with the other members in their group. For example, in a study of rats, those that played together made high-pitched squeaks that were accompanied by the release of pleasure may motivate the animals to stay together as a harmonious group even while not playing.

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