The Dutch scientists observe how birds called great tits act among each other. They compare the personalities of adult birds with those of baby birds. They also study the genetic material of the birds. This material decides how the birds will develop. It controls what they will be like. The scientists also are attempting to learn how personalities affect the survival of birds.

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Samuel Gosling teaches at the University of Texas. He says the Dutch scientists are producing the most detailed work ever done on the subject.

During the nineteen-nineties, Mister Gosling studied thirty-four hyenas at the University of California in Berkeley. The hyenas had four caretakers. Each caretaker, or keeper, answered questions about every animal. The keepers agreed about the personalities of the animals at about the same rate that people would describe other people.

The keepers described some things about the hyenas that seemed similar to humans. For example, they described some of the animals as agreeable. Others, they said, reacted with worry or even fearfulness to pressure.

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Photo courtesy Art Today

More recently, Mister Gosling studied dogs. He recently presented his findings to a meeting of the American Association for the Advancement of Science in Washington, D.C. He noted that different kinds of dogs have different personalities. But he said there also are huge personality differences within each group, or breed.

Mister Gosling developed a test for people to learn about a dog's personality. He tested seventy-eight dogs. In his study, Mister Gosling asked dog owners to rate their animal on four kinds of personality. Then he asked strangers to describe the animals. The strangers rated the dogs on their levels of energy and ability to act loving, compared with aggressiveness. They also rated the dogs on nervousness compared with calmness and intelligence compared with stupidity.

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The owners and strangers generally agreed about the personality of each dog. Mister Gosling says this shows there are such things as dog personalities. He also said his studies suggest that people should own dogs with similar personalities.

His findings provide good news for owners of dogs of unpopular breeds. For example, pit bulls have been known to attack people. Many people think of this breed as too aggressive. But Mister Gosling's work shows that each animal may have its own personality.

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Mister Gosling says one of his new projects also will involve dogs. This time, the subjects will be dogs that search for explosives. It costs a lot of time and money to train such animals. However, some dogs cannot learn this skill. If more were known about an animal's personality, choosing dogs for the training could be improved.

Samuel Gosling says the main importance of studying animal personalities is that it permits learning not possible with human beings. He said the shorter lives of animals mean that many more lives and personalities can be studied in a shorter time.

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You are listening to SCIENCE IN THE NEWS, in VOA Special English. I'm Bob Doughty with Sarah Long in Washington.

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We recently received a message from a listener in China. Wang Feng would like to know if dogs dream when they sleep.

Studies show that dogs and human beings have similar brain activity when they sleep. Researchers use a test called an electroencephalogram to study such activity.

When dogs first go to sleep, they enter a period of light sleep. This is when they can be easily awakened. In light sleep, dogs lie still and their breathing is normal.

When dogs enter deep sleep, they have difficulty waking up. Brain wave activity greatly increases. Dogs begin unusual breathing. Rapid eye movement also begins. During rapid eye movement, the eyes are moving quickly, forward and backward. Then dogs may begin to make sounds. Their bodies may make uncontrolled movements. Their legs move as if they are running. It may seem as if the dog is having a bad dream. It is best not to wake a sleeping dog. Like people, dogs need continuous sleep for healthy mental activity.

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Researchers say dogs have several dreams each night. The amount of time spent sleeping is different with each animal. Most dogs sleep thirteen to fourteen hours a day.

Researchers also say small dogs dream more than large ones. The number of dreams each animal has also is linked to many things, including age. Young dogs dream more than adult dogs.

Many people wonder what their dogs are dreaming about. Researchers believe it is likely that dogs dream in a way similar to humans. They believe dogs dream of things that are pleasing to them, but unreal. They also say dogs dream of things that happen in everyday life, such as chasing things, playing and eating.

If you are wondering, cats dream, too.

Thanks to Wang Feng for that question. We would like to hear from you. Write us at Special English, Voice of America, Washington, D.C. two zero two three seven, U.S.A. Or send electronic mail messages to special@voanews.com.

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This program was written by Lawan Davis, Ed Stautberg and Jerilyn Watson. Cynthia Kirk was our producer. I'm Bob Doughty.

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And I'm Sarah Long. Join us again next week for SCIENCE IN THE NEWS, in VOA Special English.

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