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Abstract
Domestic dogs demonstrate behavioral laterality in response to emotional stimuli;
those responses include tail wagging and head turning. The dog is the species with
the closest relationship to humans; dogs can express strong social emotions (e.g.,
attachment and separation anxiety) to specific persons, such as their owners. In this
study, we examined whether dogs demonstrate more facial laterality when reunited with
their owners than when they encounter an unfamiliar person in an unfamiliar situation.
We also examined whether the observed laterality was specific to positive social stimuli
(i.e., the owner) or a general response to nonsocial positive stimuli (i.e., toys).
The dogs' facial expressions were recorded by a high-speed video camera during the
presentation of emotional stimuli and the acceleration rates of parts of their faces
were analyzed. The results showed that the left eyebrow moved more when the owner
was present than at baseline. No bias in terms of eyebrow movement was observed when
the dogs saw attractive toys. These results suggest that dogs show facial laterality
in response to emotional stimuli. This laterality was specific to social stimuli,
probably reflecting the dog's attachment to the owner.