Third-party affective evaluation of humans by house dogs (#419)
Image scoring, or affective evaluation of third-party interactions, is a key feature of humans’ large-scale cooperative society. Here we asked whether domestic dogs evaluate humans interacting each with other over neutral objects. In two experimental conditions, the dog’s owner tried to open a container to get a junk object (a roll of vinyl tape), then requested help from an actor sitting next to her/him, while the dog watched the interaction. In the Helper condition, the actor held the container stable to help the owner to open it. In the Non-helper condition, the actor turned away and refused to help the owner. In the Control condition, the actor simply turned away in the absence of any request from the owner for help. A neutral person always sat at the other side of the owner throughout these interactions. After the interaction, the actor and the neutral person each offered a piece of food to the dog. Different groups of dogs received 4 test trials in one of the three conditions. Dogs chose food randomly in the Helper and the Control conditions, but were biased against the actor in the Non-helper condition. Importantly, the interaction between the owner and the actor involved a neutral object, not food, in which dogs showed little interest. Therefore the dogs’ avoidance of someone shown here who behaved negatively to the owner suggests a type of image scoring. This ability of ours is likely to be shared with at least one, extremely social, nonprimate species.