How Dogs Understand What We Say
Scientists — and anyone who lives with a canine — know that dogs pay close attention to the emotion in our voices. They listen for whether our tone is friendly or mean, how the pitch goes up or down and even the rhythms in our speech.
But what about the meaning of the words we say?
Sure, a few studies have reported on supersmart dogs that know hundreds of words. Chaser, a border collie in South Carolina, even learned 1,022 nouns and commands to go with them.
But otherwise, there's little evidence that dogs differentiate between speech with meaningful words and sounds that contain only inflections, says neurobiologist Attila Andics at the MTA-ELTE Comparative Ethology Research Group in Budapest.
"We know quite a bit about how much dogs get about how we say things," Andics says, "but we know quite little about how much dogs get about what we say to them."
That's about to change.
Psychologists reported Wednesday in the journal Current Biology that dogs do pay attention to the meanings of words. And they process that information in a different part of the brain from where they process emotional cues in speech.
To figure that out, graduate student Victoria Ratcliffe at the University of Sussex in England set up a clever experiment.
She brought 250 dogs into the lab. And then for each one, Ratcliffe put a speaker on either side of the dog's head.
Then she played the command "to come" out of both speakers, at the same time. At first, the command sounded normal. It had both meaningful words and emotional cues in it.
Then Ratcliffe started to manipulate the speech in the command. In some instances, she removed all of the inflections in the speaker's voice. In other instances, she kept the inflections in the speaker's voice but removed the words (or replaced the words with gibberish).
For each command, Ratcliffe recorded which way the dogs turned their heads — toward the left speaker or toward the right speaker. Even though both speakers were playing the same sounds, a clear pattern emerged.
When the dogs heard commands that still had meaningful words in them, about 80 percent of the animals turned to the right. When they heard commands with just emotional cues in them, most dogs turned to the left.
That result sounds simple. But Andics, who wasn't involved in the study, says the findings show something surprising: "that dogs are able to differentiate between meaningful and meaningless sound sequences."
The study also suggests that a dog's brain breaks up speech into two parts: the emotional cues and the meaning of the words. Then it processes these two components on opposite sides of the brain: emotional cues on the right, meaning of words on the left. (Yes, it's opposite to the way the dogs turned.)
That's a bit similar to how we humans process speech. We also break up speech into several parts, such as the meaning of the words, clues about the speaker and emotional cues.
"But with humans, it's trickier," Andics says. "We believe the human brain processes various aspects of human speech in different stages and in many different parts of the brain."
Still, though, Andics says the new study offers one way that people may be able to communicate better with their best friends: Pick the ear you use carefully.
"Tell all the emotional things to the dog in his left ear," Andics says. "For commands that you want a dog to get clearly and precisely, tell them in right ear."
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Transcript
RENEE MONTAGNE, HOST:
Dogs are better known for their loyalty and warmth than their brains. But a new study suggests they may be smarter than we think. NPR's Michaeleen Doucleff talked with some scientists about the findings as well as a representative from the canine community.
MANGO: (Barking).
MICHAELEEN DOUCLEFF, BYLINE: That's Mango. She's a German Shepherd. She lives in San Francisco, and she's my dog. Mango loves to fetch and chase squirrels. And like many dogs, she recognizes about a dozen commands. Her favorite?
DOUCLEFF: Mango, do you want to go to the park?
MANGO: (Barking).
DOUCLEFF: No matter how I say this one command... (Speaking angrily) Mango, do you want to go to the park? (In a sing-song voice) Mango, do you want to go to the park? She perks up her ears, tilts her head and...
MANGO: (Barking).
DOUCLEFF: OK, scientists know that dogs pay attention to the emotion in our voices - how the pitch goes up and down, whether the tone is friendly or mean. But I swear, with this one command, Mango understands the words. And luckily, somebody's been looking into this. There's a study out this week in Current Biology that tries to figure out if dogs really recognize words. Or are they just responding to the emotions in our voices? For instance, would Mango respond if even Google said her favorite command?
(SOUNDBITE OF GOOGLE VOICE)
GOOGLE VOICE: Mango, do you want to go to the park?
DOUCLEFF: Vicky Ratcliffe is a graduate student in the psychology department at the University of Sussex in England. She worked on the news study, and she tells me about the experiment they set up.
VICKY RATCLIFFE: The way it works is we have two speakers which are placed either side of the dog, to their left and their right.
DOUCLEFF: Then, Ratcliffe played the command to come out both speakers at the same time. At first, the command sounded normal. It had meaningful words and emotional cues in it.
(SOUNDBITE OF ARCHIVED RECORDING)
RATCLIFFE: Come on, then.
DOUCLEFF: Then, Ratcliffe changed it up. She played a command with no emotion, but meaningful words.
(SOUNDBITE OF ARCHIVED RECORDING)
ELECTRONIC VOICE: Come on, then.
DOUCLEFF: Then a command with only emotion, no words.
(SOUNDBITE OF ELECTRONIC TONES)
DOUCLEFF: Then there was one that sounded like a robot.
(SOUNDBITE OF ROBOTIC TONES)
DOUCLEFF: For each command, Ratcliffe recorded which way the dogs turned their heads, toward the left speaker or toward the right speaker. Even though both speakers were playing the same sounds, a clear pattern emerged.
RATCLIFFE: So when the dogs heard meaningful verbal information, then most of them turned to their right.
DOUCLEFF: But when the dogs heard commands with just emotional cues, most dogs turned to the left. This suggests that dogs process emotional cues on one side of the brain and the meaning of words on the other side. This is similar to how we humans process speech. Attila Andics is a neurobiologist at the Hungarian Academy of Sciences and a top expert on dog brains. He says the results are strong and clear.
ATTILA ANDICS: In a way, this study tells me that dogs are able to differentiate between meaningful and meaningless sound sequences.
DOUCLEFF: That means when Mango hears, go to the park, it's not just the emotional cues that matter to her. She's paying attention to the words I use, too. Andics says a few previous studies have hinted at this, but this new study nailed it. So back to my home version of this experiment, how will Mango respond to Google saying her favorite command?
(SOUNDBITE OF GOOGLE VOICE)
GOOGLE VOICE: Mango, do you want to go to the park?
DOUCLEFF: She's just staring at me. Nothing's happening. She's not responding at all. About 10 percent of the dogs in the study didn't respond either. So maybe Mango's not as smart as I thought. Or maybe she just knows that that computer is never going to take her to the park.
MANGO: (Barking).
DOUCLEFF: Michaeleen Doucleff, NPR News. Transcript provided by NPR, Copyright NPR.
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