Eniko Kubinyi
In most tests of general intelligence, dogs are rated as reasonably smart, but not as primates. The only place dogs beat primates is when interacting with humans. It’s not clear if dogs are better at reading human intentions or just more motivated to act on them, but dogs really seem to do that. to get us.
Now researchers in Hungary have tested dogs’ willingness to cooperate with us by sitting them still in an MRI machine. By monitoring the dogs’ brain activity, the researchers were able to determine that dogs can recognize not only words, but also the emotional tone behind them. Dogs recognize when both words And tone indicates praise. Then they feel rewarded.
The work was carried out by a group of researchers in Budapest, which becomes important when we get to the words the dogs responded to. The hypothesis behind their work: Dogs can recognize both the meaning of what is being said (technically the lexical content) and the intonation used to say it. In other words, it’s not enough to say “good boy” to your dog — you have to sound like you mean it.
To test this hypothesis, the authors had dogs sit still in an MRI tube. The MRI performed functional scans, which identify those areas of the brain that see an increase in activity after a stimulus. The stimuli in this case were spoken words. For controls, the authors have included some conjunctions, such as “akár” (meaning “as if” without, presumably, the sarcastic implications). These words were recorded in both a neutral tone and a higher register, similar to what is commonly used to indicate praise.
Separately, a group of positive statements such as “‘ɒzɒz” (“that’s it”) and “‘yɟɛʃ” (“smart”) were included in both neutral and laudatory tones. Non-speakers of Hungarian who were asked to rate the recordings agreed that the laudatory tone came across, even though the meaning of the words was unclear.
In humans, the left side of the brain is specialized for identifying meaning in spoken words. This also seems to apply to dogs. Areas on the left side of the human brain respond specifically to words or phrases used to convey praise. In contrast, the Hungarian experiment showed no indication of increased activity in dog brains when the conjunctions were played. This suggests, in the authors’ words, “that dog brains retain intonation-independent lexical representations of meaning.”
The auditory systems of the dogs tested also picked up the tone, but in this case it was an area on the right side of the brain that was activated. This showed increased activity in response to both praise and neutral words, but there was a difference between the two: responses were stronger to neutral words.
However, the most compelling result came when the authors looked at the brain regions used to process rewards. Here, merely hearing words of praise was not enough to induce increased activity. Hearing a conjunction in a pleasant tone didn’t either. The reward centers lit up only when both tone and words were consistent with praise. In other words, both the right and left sides of the brain had to agree to hear praise so that the dog would get a sense of reward.
This interpretation may sound a bit far-fetched, given that the dogs couldn’t really respond to the praise. But earlier this month, another team published a paper that also placed dogs in an MRI scanner. In that study, the authors also looked at dogs’ neurological reward centers to measure their dogs’ response to food or praise from their owners. The extent to which their owners reacted more strongly was found to be predictive of the dogs’ behavior when they were placed in a T-shaped room with their owner on one arm and the food in the other.
In other words, if the dogs’ brains reacted more strongly to their owners’ praise, the dog would probably run to the owner instead of food. (The owner: Food ratings varied between the 15-dog group tested, so mileage with your own dog is impossible to predict.)
Previous studies have shown that dogs can recognize words; it is estimated that they can track up to 1,000 different words associated with items and can retrieve the correct item on command. But that is a relatively simple form of association. The work here suggests that dogs can actually perceive the meaning of certain bits of human speech.
The authors argue that this tells us something about mammalian cognition in general and about ourselves in particular. Since humans process meaning using both the left and right sides of the brain, our use of language may be just an elaboration of a basic mammalian trait. “Lateralized lexical processing does not seem to be a uniquely human ability resulting from the emergence of language,” they conclude, “but rather an older function that can be exploited to associate arbitrary sound sequences with meanings. So what makes lexical items uniquely human is not the neural capacity to process them, but the invention to use them.”
Science2016. DOI: 10.1126/science.aaf3777 (About DOIs).
Social cognitive and affective neuroscience2016. DOI: 10.1093/scan/nsw102 (About DOIs).