Researchers with the group Canine Mind examined how the hormone oxytocin affected the behavior of dogs. The team found that oxytocin altered the emotional states of the dogs, making them feel more relaxed and less threatened. The dogs also became much more interested in looking at happy human faces as opposed to angry ones.
For the study, the research team showed the images of smiling and angry human faces to 43 dogs. Each dog was analyzed once after oxytocin had been administered and once without oxytocin. The researchers used an eye-tracking device to monitor the dog’s gaze and pupil size.
According to the experts, emotions and attentiveness control the dog’s gaze and regulate pupil size, so eye tracking can provide insight into the minds of dogs.
Dogs usually focus on the most exceptional condition of any given situation. For example, in a frightening setting, dogs typically focus on threatening activity. Recognizing threats as quickly as possible is important for the animals’ survival. However, the study revealed that dogs under the influence of oxytocin were much more drawn to smiling faces than angry ones.
“It seems that the hormone oxytocin influences what the dog sees and how it experiences the thing it sees,” explained Sanni Somppi, a doctoral student at the University of Helsinki.
Oxytocin was also found to influence the emotional states of the dogs, which was reflected in their pupil size.
“We were among the first researchers in the world to use pupil measurements in the evaluation of dogs’ emotional states,” said lead researcher Professor Outi Vainio. “This method had previously only been used on humans and apes.”
When the dogs were not under the influence of oxytocin, their pupils were largest while looking at angry faces, indicating that angry faces would normally evoke the strongest emotional reaction in the dogs. But under the influence of oxytocin, smiling faces affected the emotional states of the dogs more than angry ones.
The researchers explained that oxytocin most likely made the angry faces seem less threatening while the smiling faces seemed more appealing.