Anyone who's had a canine best friend knows that dogs are attuned to human emotions. If you're sad, your dog will put its head on your knee or snuggle up. It might whine and give you a friendly lick.
Dogs also seem to sense emotions in people they don't know. Take a dog into a nursing home or children's hospital, and it will find those who need cheering up.
Is there a biological explanation for dogs' ability to read human emotions, or is the empathy a natural result of how closely dogs and humans live these days?
The answer is a combination of the two.
The relatively new field of canine neuroscience investigates the workings of a dog's brain. In February 2014, the results of a study by a team of Hungarian researchers were published in the journal Current Biology and reported in popular news media. Using fMRI (functional magnetic resonance imaging), the scientists found that dogs' brains have a small part dedicated to detecting emotions in the voices of humans and other dogs. Humans have a similar brain part that enables them to sense emotions from human sounds, regardless of words. Their findings led the scientists to believe that dogs can tell by the sound of a voice when a person is sad [source: Doucleff]. (There's a fascinating side story about how the scientists got 11 dogs to enter a scanner and stay still.)
Is there more to the story than detecting the sounds of voices? Probably so. In 2004, a Harvard scientists said that his research showed that over the centuries of living closely with and depending upon humans, dogs have adapted genetically, developing a keen ability to read human emotions and intentions [source: Economist].
Whatever the explanation, there's nothing like a sympathetic pooch to lift the spirits.