It's not difficult for a dog to be able to pick up when you're ticked off at them. You might shout, adopt a dominant stance and lower the tone of your voice to let dear Fido know that peeing in your shoes is not OK. But can they tease apart a grin from a grimace?
Dog owners would probably say yes, but that's not enough to convince the scientific community. Eager to find out, scientists began to probe our canine companion's capabilities. According to their newly published research, pooches can indeed discern a happy face from an angry face in the absence of other cues.
But before you shout "No duh," science requires more than just anecdotes and doggy owner vibes as evidence. Studies had also tried to examine this ability before, but none of them produced particularly convincing results. Furthermore, according to the team, this is the first study to demonstrate that animals, other than humans, are able to discriminate between the emotional expressions of a different species, or heterospecific if we're being technical.
For the study, which has been published in Current Biology, scientists in Vienna trained dogs to discriminate between happy and angry faces. They did this by presenting a variety of different breeds with 15 picture pairs of people making both expressions, whereby one group was shown only the top half of the face and the other was shown only the bottom half.
Next, they probed their ability to tell apart expressions through a series of four different trials. These involved presenting the dogs with either the same or the other half of the face shown in training but using a novel face, using the other half of the same face used in training, or showing them the left half of the face used in training.
The researchers found that the dogs who were rewarded with a treat for selecting the happy face learned the discrimination faster than dogs rewarded for selecting the angry face. The authors note that this would be expected if the dogs recognized these angry expressions as an unpleasant, or aversive, stimulus.
Furthermore, they were also able to select the right face with between 70-80% accuracy, which is above what we would expect by random chance. This means that not only were the dogs able to learn to identify these different expressions, but they could also transfer what they learnt to new cues.
Although previous studies have hinted at the ability of dogs to distinguish between expressions, the investigations used whole faces, so the dogs could have been recognizing repeated features such as a flash of pearly whites in a smile, rather than the expression itself. According to the researchers of the new study, identifying different emotions from only parts of the face calls for a more holistic understanding.
While it seems that dogs may be able to tell that these two facial expressions have different meanings, what those meanings are for the dogs is difficult to know. But the researchers say it's likely that they associate grins with a positive meaning and frowns with something negative that they should avoid.
[Via Current Biology, Cell Press, Science and The Verge]
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