We assessed how water rescue dogs, which were equally accustomed to respond to gestural and verbal requests, weighted gestural versus verbal information when asked by their owner to perform an action. Dogs were asked to perform four different actions ("sit", "lie down", "stay", "come") providing them with a single source of information (in Phase 1, gestural, and in Phase 2, verbal) or with incongruent information (in Phase 3, gestural and verbal commands referred to two different actions). In Phases 1 and 2, we recorded the frequency of correct responses as 0 or 1, whereas in Phase 3, we computed a 'preference index' (percentage of gestural commands followed over the total commands responded). Results showed that dogs followed gestures significantly better than words when these two types of information were used separately. Females were more likely to respond to gestural than verbal commands and males responded to verbal commands significantly better than females. In the incongruent condition, when gestures and words simultaneously indicated two different actions, the dogs overall preferred to execute the action required by the gesture rather than that required verbally, except when the verbal command "come" was paired with the gestural command "stay" with the owner moving away from the dog. Our data suggest that in dogs accustomed to respond to both gestural and verbal requests, gestures are more salient than words. However, dogs' responses appeared to be dependent also on the contextual situation: dogs' motivation to maintain proximity with an owner who was moving away could have led them to make the more 'convenient' choices between the two incongruent instructions.
Keywords: Gestural cue; Human–dog communication; Incongruent information; Verbal cue; Water rescue dog.