By Nell Greenfieldboyce, NPR

When you praise a dog, it’s listening not just to the words you say but also how you say them.

That might not be huge news to dog owners. But now scientists have explored this phenomenon by using an imaging machine to peek inside the brains of 13 dogs as they listened to their trainer’s voice.

The reward pathway in the dogs’ brains lit up when they heard both praising words and an approving intonation — but not when they heard random words spoken in a praising tone or praise words spoken in a flat tone, according to a report in the journal Science.

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