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阅读下列短文，从下面每小题的A、B、C、D四个选项中选出最佳选项。 Why are dogs our best friends? Maybe because they can understand our words much better than we thought, according to a study in Hungary. It found that dogs understand not only what we say, but also how we say it.
"The results were very exciting and very surprising," said the researcher Attila Andies, from Eotvos Lorand University in Budapest.
For the study, the researchers first trained 13 dogs for months. The dogs had to sit quietly inside machines, so that the researchers could check their brain activity.
Then the researchers put headphones on dogs and played people's voices to them. There were four different voices. Some were positive words, such as "well done", or neutral (不带感情色彩的) words like "however". The words were also in different tones (音调). Some were positive and some were neutral.
Brain scans (扫描) showed that the dogs could recognize words, as well as the tone of words, much like people do. The positive words with a positive tone brought the stronger activity in their brain's reward centres (反应中枢).
"It shows that for dogs, a nice phrase can work very well as a prize, but it works best if both words and tones match," said Andies.
They also found that dogs deal with meaningful words with the left side of the brain and tones with the right. Human brains work in the same way.
"It gave us a new understanding of language," said Andies. That is, not only do humans understand the meaning in words, other species (物种) do too.
