Humans typically act according to unwritten social rules: when someone beckons another person over, that person approaches; when someone is waved away, they leave. Researchers at the Messerli Research Institute at Vetmeduni investigated whether other animals share our expectations about gestures. Using domestic dogs (Canis familiaris), they examined what happens when humans violate the familiar rules of everyday nonverbal communication.
A precise and in-depth look into dogs’ eyes
In an eye-tracking study of 39 pet dogs, the scientists investigated whether their eye movements and pupil sizes respond when they observe a deviation from the usual reaction to conventional human communicative gestures. In the eye-tracking experiment, the dogs watched various videos of two actresses responding to familiar gestures such as “come here” and “go away.” Sometimes the response was as expected; at other times it was unexpected, inappropriate, and incongruent. For example, one actress walked away after being called over, or approached after being waved away by a second actress.
Dog pupils dilate in response to inappropriate human behavior
While the dogs watched the videos attentively irrespective of the congruent or incongruent reaction of the actress, their pupil size varied significantly depending on the reaction. Lead author Lucrezia Lonardo of the Messerli Research Institute explains: “The dogs’ pupils dilated more when one of the actresses responded in an unexpected way compared to when she responded in the expected way. Such physiological response is a subtle sign of surprise or increased attention.”
Dogs may possess substantial knowledge of human social behavior
The researchers suspect that, over the course of their development, pet dogs implicitly form expectations about the typical responses to certain conventional human gestures. “Our findings suggest that dogs can learn the unwritten rules of human interaction through daily cohabitation with us. Remarkably, they responded even when merely observing two unfamiliar humans interacting – which indicates that dogs may understand more about human social behavior than we realize”, Lonardo concludes.
The study „Pupil size changes reveal that dogs are sensitive to the social conventions behind human gestures“ by Lucrezia Lonardo, Christoph J. Völter and Ludwig Huber was published in „Cognition”.
Scientific contact:
Lucrezia Lonardo, PhD.
Messerli Forschungsinstitut für Mensch-Tier-Beziehung
Veterinärmedizinische Universität Wien (Vetmeduni)
Lucrezia.Lonardo@vetmeduni.ac.at