If you blink at me, I'll blink back. Domestic dogs' feedback to conspecific visual cues.

Blinking, along with other facial expressions, has been suggested to play a role in dogs' intra- and interspecific communication, however the feedback this signal elicits from the audience is still poorly studied. In this study, we investigated the behavioural and physiological responses of 54 domestic dogs to videos of conspecifics performing blink. Based on existing literature, we hypothesized that dogs would show a higher rate of blinking when exposed to blink than to another facial expression (nose lick) and to an attentive still-looking face (control). Results showed that dogs blinked more during the blink video compared to the nose lick (NL) video, suggesting a mimicry phenomenon and implying a possible role of blinking in dogs' communication. Cardiac analyses showed increased heart rate variability values during the video sessions independently to the type of facial signal projected, suggesting that the stimuli were not perceived as stressful. The present results open the door to future investigation of blink synchronization, as this aspect was not directly addressed in the present study. Future research should also explore the effects of eye blink and NL in modulating intraspecific social interactions.