Editor’s Note: This article is from our Science for Kids series, aimed at children in grades 4-8.
Have you ever wondered if your dog could tell how you felt? New research shows that dogs can tell whether people are angry or happy just from their facial expressions.
Researchers in Europe –Vienna, Austria to be exact– studied the way dogs reacted when they were shown photos of human faces. In each picture, the person was either smiling or frowning. The study found that dogs could distinguish between the angry and happy expressions on a human face.
It is the first study to show an animal other than a human can tell the difference between emotions expressed in a different type of animal.
“Our study demonstrates that dogs can distinguish angry and happy expressions in humans, they can tell that these two expressions have different meanings, and they can do this not only for people they know well, but even for faces they have never seen before,” said Ludwig Huber, senior author and head of the group at the University of Veterinary Medicine Vienna’s Messerli Research Institute, in a press release.
In the study, dogs were presented with a series of photographs of the same person making either a happy or angry face. Some dogs were only presented with pictures of the upper half of the face, while others were shown the bottom half. This was to rule out the possibility that the dogs made their decision based on seeing frown lines or teeth.
The researchers then used four different types of photos to test the dogs’ ability to discriminate between the angry and happy faces. Sometimes they used only the upper or lower part; sometimes they used the left half.* Sometimes the dogs saw a familiar human face, and sometimes they saw someone new. The dogs did not have a problem distinguishing emotions even in people they did not know. This showed researchers that dogs could not only learn to identify facial expressions, but they could also apply that to new face.
Some of the dogs were rewarded for choosing the angry faces, while others were rewarded for choosing the happy faces. The dogs that were rewarded for choosing the happy face learned faster than the dogs that were rewarded for choosing the angry face. This means that the dogs associated positive meaning with the happy faces while associating negative meaning with the angry faces, according to Huber.
The study suggests the dogs had formed memories by living and interacting with humans on a regular basis. If this is true, it’s possible the dogs learned how to discriminate between the two emotions prior to the experiment.
According to the study, it is a popular belief that animals can experience emotions similar to the emotions in humans. Animals may be able to anticipate the emotional response in another species and react accordingly. This could help an animal survive or compete for food. For example a predator, like an eagle, could tell whether or not its prey, like a rabbit, is expressing fear.
More research may help scientists understand how dogs respond to other emotions in people and other animals. Further studies will help scientists uncover how emotion plays an important role in adaptation, or how animals change their behavior over time.
At this point in time, the researchers cannot necessarily determine what factors play a role in the dogs’ ability to discriminate between the two emotions. In fact, the study itself led to more questions to be answered.
“As is often with scientific studies, our study raises more questions than it answers,” Dr. Corsin Müller, the author of the study, said in an email.
*A previous version of this story incorrectly indicated that the dogs were shown the right half of the face during the study when only the upper, lower, and left half were shown.