You can't help it. You see that sweet little face and immediately begin to blabber in a sing-song voice, "Hello, sweetie pie! Who's a good boy?!"

We tend to talk to puppies as we do to babies, speaking slowly in a high-pitched voice. An international team of researchers recently looked at the science behind what they call "dog-directed speech" to find out why we do it and if our canine friends truly respond to it.

When we talk to babies, we speak more slowly, using a higher and more variable pitch, the researchers say. We also tend to articulate our vowels more clearly than when we're talking to adults. This "infant-directed speech" engages and maintains the attention of babies as young as 7 weeks old, who prefer it over normal adult speech. Researchers decided to apply the same rules to dogs.

The 'sweetie pie' experiment

For the first part of the experiment, people were asked to say the phrase, "Hi! Hello cutie! Who's a good boy? Come here! Good boy! Yes! Come here sweetie pie! What a good boy!" while looking at photos of puppies, adult dogs, older dogs and then while looking at no photos. The researchers then analyzed the recordings to see how speech patterns changed while people were speaking to different aged dogs.

They found that the volunteers used higher-pitched, slower-tempo speech with the pitch varying when talking to the dogs. The most obvious change was with puppies, when the volunteers increased their pitch by 21 percent on average compared to normal speech. (Their pitch increased on average by 11 percent when they spoke to adult dogs and 13 percent with old dogs.)

The results, which involved researchers from the U.S., the U.K. and France, were published in the journal Proceedings of the Royal Society B.

Puppies like 'puppy talk'

Puppies are more reactive to dog-directed speech, and their response to the higher pitch is a key reason why. Golden Pixels LLC/Shutterstock

For the second part of the experiment, the recordings were played for puppies and adult dogs. The researchers found that the puppies responded more strongly to the dog-directed recordings than the adult dogs. For example, they reacted more quickly to those recordings, looking more frequently at the speaker and approaching it closer and for longer periods of time. Adult dogs in the experiment didn't seem to have a preference how people spoke to them.

"One of the hypotheses was that we humans use this dog-directed speech because we are sensitive to the baby cues that come from the face of a small baby [animal] as we are sensitive to the faces of our babies," study co-author, psychology professor Nicolas Mathevon of the University of Lyon/Saint-Etienne, told BBC News.

"But actually our study demonstrates that we use pet-directed speech or infant-directed speech not only because of that, but maybe we use this kind of speech pattern when we want to engage and interact with a non-speaking listener. Maybe this speaking strategy is used in any context when we feel that the listener may not fully master the language or has difficulty to understand us."

Another take on puppies versus adult dogs

Dogs especially prefer listening to people who use dog-directed speech and dog-related content. SG SHOT/Shutterstock

A more recent study replicated much of the earlier one, but had slightly different results. Researchers had various women record "Shall we go for a walk?" when speaking directly to a dog, puppy and a baby. Then they played those recordings for 44 adult pet dogs and 19 puppies. The results were published in the journal Scientific Reports in July 2017.

Researchers found that adult dogs responded more attentively to speech directed to pets, than speech directed toward adults. Puppies responded the same to any kind of speech.

The study's lead author Sarah Jeannin told Seeker that there were differences between the two experiments. In the first, the sample size was smaller and the women were recorded while they were speaking to pictures of dogs, versus real dogs.

The results didn't surprise her, Jeannin said.

“I decided to set up this experiment precisely because I noticed that dogs were more attentive to people when they were talking using this high-pitched voice."

Researchers published a similar study in March 2018, finding that adult dogs preferred high-pitched "dog-directed speech."

They had people talk to dogs directly in both "dog speak" and the way people talk to each other. In addition they used dog-directed speech, such as "you're a good dog," as well as words that should have little meaning to canines, like "I went to the cinema last night."

“We wanted to look at this question and see whether social bonding between animals and humans was influenced by the type and content of the communication,” study co-author Dr Katie Slocombe from the University of York’s Department of Psychology, said in a statement.

The researchers found that the dogs were more likely to want to interact and spend time with the people who used dog-directed speech and dog-related content. The study was published in the journal Animal Cognition.