28 November 2022
Dogs can tell whether you’re happy or sad based on the tone of your voice, according to an emerging field of canine neuroscience. Researchers at Eötvös Loránd University in Hungary have been using fMRI (functional magnetic resonance imaging) technology to peer inside dogs’ minds for the past few years.
They have recently experimented with playing different sounds to the dogs in the scanner. Their paper, published in Current Biology, shows that dogs’ brains have a dedicated area that responds more to voices (human speech or dogs barking) more than other meaningless sounds (such as glass breaking). Furthermore, a portion of this area is more active when a sound is emotionally positive than a negative sound.
This suggests dogs can distinguish between happy and sad sounds when they hear these noises, but it’s unclear what exactly is going on in their minds.
It’s already known that human brains have a precise area within the primary auditory cortex which responds more to a human voice than to non-vocal noises and that it reacts differently depending on the emotional valence of the voice, i.e., whether it expresses happiness, sadness, anger, or other emotions. This explains our reliance on spoken language for communication results.
Next, the researchers wanted to see if dogs’ brains had similar structures in the fMRI machine. Each dog was kept in the scanner for six minutes as part of the investigation. Then, they played roughly 200 sounds: human voices, dog vocalizations, and meaningless noises, tracking their brain activity as they listened to each type. The dogs were also scanned in silence. As a comparison, 22 human participants also participated in the same experiment.
Their study discovered that some regions of the dogs’ brains respond more to vocalizations (whether from other dogs or humans) than non-vocal sounds.
The underlying vocal recognition area is likely to have evolved around 100 million years ago in a common ancestor of humans, dogs, and other placental mammals. This brain area may explain why mammals have been so evolutionarily successful by enabling some key mammal characteristics – a high degree of communication and social structure.
It makes evolutionary sense for dogs to be attuned to other dogs’ communication and to all sorts of noises. However, because humans have selectively bred dogs to get along with us best, it makes sense that their auditory intelligence is involved in interpreting our vocal signals.
A more intriguing finding of the experiments was that dogs’ brains showed different types of activity depending on whether the sounds they heard were happy or sad, whether they came from humans or dogs. For example, certain areas of their auditory cortex consistently showed more activity when they listened to happy sounds, such as recordings of a human laughing or a dog barking when its owner returned home.
We cannot fully understand dog cognition by observing a correlation between an external stimulus and a specific type of brain activity. For example, dogs can differentiate between meaningless noises and vocal communication and recognize that a cry conveys a different message than a laugh.
It’s unclear at the moment whether this emotional sensitivity is a learned behavior – the result of living with and training humans – or an evolutionary adaptation created by generations of selective breeding. Regardless, it opens up a new research direction researchers plan to pursue.