Dogs have an uncanny ability to pick up on our mood—whether happy, sad, or angry—seeming to sense our emotional currents through changes in the tone of our voice. Ask dog owners—many will agree. It’s the result of millions of years of evolution and thousands of years of breeding, and after all that time, we’re beginning to understand the neuroscience that underpins their apparent devotion.
It took a while to get there, though. Scanning other animals is normally very difficult. Usually, they need to be anesthetized. Fortunately, dogs are eminently trainable. Attila Andics, a researcher in the MTA-ELTE Comparative Ethology Research Group in Budapest, and his team trained 11 dogs, all border collies and golden retrievers, to rest in an MRI machine. That allowed them to observe the patterns in the dogs’ brains when they heard any of 200 different sounds and compare those responses to humans’. The study is the first to make such a direct neurological comparison between humans and an a non-primate animal.
Andics and his colleagues reported in Current Biology that one region of the dog brain responds to vocalizations of its own species, while another responds to generic emotional vocal cues.
Virginia Hughes, writing at Only Human:
The researchers found some notable differences between dog and human brain responses. In people, just 3 percent of our auditory cortex responds more strongly to non-voice sounds than to voice sounds. In dogs, it’s 48 percent. “The human auditory system is optimized to process vocal sounds, and the dog auditory brain in general is not as specialized,” Andics says. As to the implications of that difference, who knows. He speculates that it could be what allowed us to develop language.
Andics is more excited about the ways in which the dog and humans brains are similar. It turns out that both species have an area of the brain that is tuned to the “emotional valence” of a voice, meaning it responds more strongly to positive emotions than negative emotions. And for this region, it doesn’t matter whether the voice is human or canine; a burst of laughter is equivalent to a playful bark. This result agrees with a study his team published last month showing that certain acoustic properties convey emotion in both human and dog sounds. The shorter the burst of a call, for example, the more positively it is perceived.
It’s easy to read into this finding too far, and it’s important to keep in mind that scientists disagree on what it means. Evolutionary biologists argue that dogs and humans can’t have received their vocal-perception strategies from a common ancestor—if they did, then many other mammals would have to have it, too.
Andics argues that it’s possible that other mammals do have such a system, since recognition of emotional cues through vocalizations would have been beneficial to all of them. Others say that this is merely another example of convergent evolution—the independent evolution of certain characteristics in species of different lineages. Hughes’ article dives into more detail about the varying theories and explores the future of dog research.