If you want to keep your emotional life a secret from everyone, then the research is pretty clear—don’t get a dog. They are just too skilled at interpreting how we are feeling. Previous research has shown that dogs can recognize emotions in people’s facial expressions—they are able to distinguish emotional facial expressions from neutral expressions and they can tell happy faces from angry ones. There has been less research on dogs’ ability to distinguish between different emotions that are conveyed through auditory means, but we do know that they can match happy and angry faces to vocalizations that match those emotions.
Researchers interested in dogs’ ability to detect emotions with their ears studied the way that dogs’ brains process human sounds that carry emotional information—specifically which side of the brain they used. The reason that anyone cares about the side of the brain they use is that many previous studies have shown that dogs use different sides of the brain to process information depending on the emotions involved. Generally speaking, stimuli associated with positive emotions are processed in the left side of the brain while those with negative emotions are processed in the right side of the brain.
In a recent study, experts in the field of brain lateralization found that dogs process non-verbal human vocalizations predictably based on the emotional content of the sounds. Dogs tend to process sounds with positive emotions such as happiness in the left side of their brains and sound with negative emotional content such as fear and sadness in the right side of their brains.
The set-up for studying auditory processing is delightfully simple. Researchers played a sound simultaneously through two speakers on opposite sides of each dog’s head and observed which way the dog turned her head in response. (Dogs, like humans, control each side of the body with the opposite side of the brain. Therefore, a dog who turns her head to the right is indicating that she is processing a sound with the left side of her brain and vice versa.) To make sure that the dogs are at the same distance from each of the speakers, they are given a bowl of food in the proper location centered between the speakers and while they are eating, the sounds are played.
Dogs’ responses to people’s non-verbal vocalizations followed the usual pattern of brain lateralization, responding differently depending on the emotional content of the sounds. Dogs consistently turned to the left in response to sounds that conveyed fear and sadness, and the same was true for anger but to a lesser extent. Dogs consistently turned to the right in response to vocalizations conveying happiness. The final two emotions—surprise and disgust—did not show a significant pattern. The emotions studied are considered the six basic emotions and it is common to study them as a set like this.
The next time you are laughing or crying, remember that these sounds are meaningful to your dogs, and that their brains react accordingly.