Behavioural Analysis of Dogs' Response to Threatening and Neutral Conspecific Video Stimuli

Dogs' displacement behaviours and some facial expressions have been suggested to function as appeasement signals, reducing the occurrences of aggressive interactions. The present study had the objectives of using naturalistic videos, including their auditory stimuli, to expose a population of dogs to a standardised conflict (threatening dog) and non-conflict (neutral dog) situation and to measure the occurrence of displacement behaviours and facial expressions under the two conditions. Video stimuli were recorded in an ecologically valid situation: two different female pet dogs barking at a stranger dog passing by (threatening behaviour) or panting for thermoregulation (neutral behaviour). Video stimuli were then paired either with their natural sound or an artificial one (pink noise) matching the auditory characteristics. Fifty-six dogs were exposed repeatedly to the threatening and neutral stimuli paired with the natural or artificial sound. Regardless of the paired auditory stimuli, dogs looked significantly more at the threatening than the neutral videos (?(2)((56, 1)) = 138.867, p < 0.001). They kept their ears forward more in the threatening condition whereas ears were rotated more in the neutral condition. Contrary to the hypotheses, displacement behaviours of sniffing, yawning, blinking, lip-wiping (the tongue wipes the lips from the mouth midpoint to the mouth corner), and nose-licking were expressed more in the neutral than the threatening condition. The dogs tested showed socially relevant cues, suggesting that the experimental paradigm is a promising method to study dogs' intraspecific communication. Results suggest that displacement behaviours are not used as appeasement signals to interrupt an aggressive encounter but rather in potentially ambiguous contexts where the behaviour of the social partner is difficult to predict.