Scientists have found evidence to support what many dog owners have long believed: man's best friend really does understand some of what we're saying.
Researchers in Hungary scanned the brains of dogs as they were listening to their trainer speaking to determine which parts of the brain they were using.
They found that dogs processed words with the left hemisphere, while intonation was processed with the right hemisphere — just like humans.
What's more, the dogs only registered that they were being praised if the words and intonation were positive; meaningless words spoken in an encouraging voice, or meaningful words in a neutral tone, didn't have the same effect.
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"Dog brains care about both what we say and how we say it," said lead researcher Attila Andics, a neuroscientist at Eotvos Lorand University in Budapest. "Praise can work as a reward only if both word meaning and intonation match."
Andics said the findings suggest that the mental ability to process language evolved earlier than previously believed and that what sets humans apart from other species is the invention of words.
"The neural capacities to process words that were thought by many to be uniquely human are actually shared with other species," he said. "This suggests that the big change that made humans able to start using words was not a big change in neural capacity."
While other species probably also have the mental ability to understand language like dogs do, their lack of interest in human speech makes it difficult to test, said Andics.
Dogs, on the other hand, have socialized with humans for thousands of years, meaning they are more attentive to what people say to them and how.
The study was published in the journal Science.
Andics also noted that all of the dogs were awake, unrestrained and happy during the tests. "They participated voluntarily," he said.