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Humans tend to use a kind of "baby talk" when speaking to dogs of all ages, says a new study by an international team of researchers, although only young dogs react positively to it.

The team, led by bioacoustician Nicolas Mathevon of the University of Lyon in France, set out to learn how dogs respond to human speech by recording the voices of 30 women as they read from a script with phrases like "Hello cutie! Who's a good boy?" both with and without a picture of puppies and older dogs placed in front of them.

Then they took the recordings to a New York City animal shelter, where they played them for a group of puppies, which reacted excitedly, barking and running toward the loudspeaker – and a group of older dogs, which responded with no more than a quick glance.

"Dogs have been selected by humans for centuries to interact with us," Dr. Mathevon told the BBC. "Maybe we have selected puppies that want to play or engage in interaction with us."

"And maybe older dogs do not react that way because they are just more choosy and they want only to react with a familiar person."

The study also offers a different take on why humans use "baby talk" for young animals, suggests Mathevon. Instead of the "baby schema" model, which argues that we're moved by the big eyes and awkward movements of baby-like cute animals, says Mathevon, it might be a natural response to an unconscious belief that the listener has difficulty understanding us.

"Maybe this register of speech is used to engage interaction with a non-speaking [animal] rather than just a juvenile listener," he told the BBC.

The study, published in the Proceedings of the Royal Society B, follows one produced by another team of researchers that showed how human speech was processed in the canine brain, as º£½Ç´óÉñ’s Lucy Schouten reported in August:

Dogs also have sharper memories than we might suspect, too, as the Monitor’s Eva Botkin-Kowacki reported in November:

The present study by Mathevon and his colleagues doesn’t indicate whether puppies’ response to puppy talk is innate or learned, as Science magazine notes.

But our habit of treating dogs – even older ones – like human infants, Oregon State University animal behaviorist Monique Udell told the magazine, might be "an important part of their success in human environments."