For decades, scientists have believed that a big shift occurred in human evolution that made our brains left hemisphere dominant in processing communication, and that this is what led to the evolution of our unique language abilities, says Brian Hare, a cognitive neuroscientist at the Duke Institute for Brain Sciences in Durham, N.C.
All the dogs in the study were willing volunteers and were trained to lie still in the scanner using a training method developed by Marta Gacsi. The dogs could get up and leave the machine whenever they wanted. But it was clear to the dogs that their human companions loved it when they did this very easy task.
He says most dog owners have experimented with trying to “trick” their dogs by saying nonsense words in a cheerful, happy tone of voice. “I think the big difference here is that they only heard us, they didnt see us,” says Andics, because the dogs were inside the machine. “Here, the only information they had was the speech signal. What we saw is that for praise to be processed as a reward, when there is no other supporting information, both word meaning and intonation have to fit.”
He says people have been studying great apes and fossils to try to figure out exactly when that left hemispheric shift occurred. “It seems the story is really that there is a general mammalian bias to process words or meaning in communication in the left hemisphere and it became exaggerated in humans,” says Hare. “Its not something completely new to our species.”
Whats more, he says, this study is important because he thinks its the first major finding using noninvasive neuroscience with awake animals — usually they have to be drugged or restrained. “That just changes everything,” he says. “You literally can see whats going on in their brains just like you would with people. And its really the first time that this has led to a big discovery and I think were going to see a lot more of this.”
The team also found that regardless of the word meaning, when the dog listened to neutral tones, there was increased activity in a region of the right hemisphere in the pup’s brain. According to the authors, this region is specifically designed to process generic acoustic information. A subsequent analysis showed that the lower frequencies characteristic of neutral tones elicited the greatest responses—a result that also mirrors auditory processing in humans, macaques and previous dog studies.
A team of Hungarian neuroscientists has shown that dogs process certain aspects of speech similar to the way humans do, with specialized brain areas dedicated to discriminating both the meaning of words (what we say) as well as the tone in which they are delivered (how we say it). This shared neural circuitry between two species, the authors suggest, is evidence that the development of language in humans might have been a learned invention and not the product of unique changes in our brains.
In the study, Andics and his team brought 13 pet dogs to their laboratory, and trained them to remain still in an fMRI scanner—a claustrophobic space for even the most well-behaved canine. While their brain activity was monitored, the dogs listened to an audio recording with a variety of familiar praises (e.g. “well done,” “clever,” and “thats it”) as well as neutral conjunctions that are commonly used in everyday speech but had no relevant implications for the dogs (e.g. “as if,” “such,” “yet”). To determine whether the dogs could discriminate between the “what” of the word versus how we say it, each word was spoken in either a praising intonation—characterized by a higher, more varying pitch (i.e. how you might talk to a cute toddler)—or a neutral intonation.
It’s easy to conclude that, because dogs process verbal and nonverbal information in speech similar to the way we do, they likewise understand what they are hearing. But this would be a vast oversimplification. The study “shows that dogs are capable of identifying strings of phonemes that form meaningful speech commands, rather than solely relying on the commands intonation,” says David Reby, a psychologist at the University of Sussex whose previous behavioral studies in dogs also identified parallels in speech perception between humans and dogs. “It does not, however mean that dogs are capable of understanding human language.”
Others dont agree that specialized speech processing was an original feature in dogs, asserting that they may have evolved this ability as they became domesticated.
Over several months, the team had trained the dogs to lie in a functional magnetic resonance imaging (fMRI) scanner and remain completely still for two 7-minute brain-scanning sessions. The dogs were not restrained and could leave the scanner whenever they chose.
Others urge even greater caution in interpreting the results. Gregory Berns, who studies brain activity in dogs and people at Emory University in Atlanta, Georgia, faults the relatively small number of animals and the reporting of only averaged data. Berns argues that the authors failed to test whether individual dogs had inherent biases to greater activity in one hemisphere over the other, independent of language. Variability in even a single dog could have skewed the averaged results, he says.
Parts of the right hemisphere, meanwhile, picked up on the emotional information conveyed by the intonation, regardless of a word’s meaning. The researchers found that words delivered in a praising tone were associated with stronger coordination of activity between certain auditory regions and areas involved in reward processing.
Study suggests that man’s best friend probably understands more than we thought when we talk to them.
But David Reby, a psychologist at the University of Sussex, UK, calls the work “an elegant study”, noting that it corroborates his own behavioural findings in dogs3.