In this study we aimed to investigate novel aspects of dogs’ comprehension of human social behaviours by revealing potential differences in the responses of wolves and dogs when they interact with a human in socially ambiguous situations.

In Experiment 1, pet dogs (N = 13) and hand-reared wolves (N = 13) encountered a stranger who approached them first in a friendly, then a threatening way, and finally switched back to friendliness again (Approaching stranger; AS) while the passive owner/caregiver was standing close to the subjects. In contrast to dogs, wolves avoided eye contact with both the caregiver and the stranger, however, only dogs showed aggressive displays towards the stranger.

In Experiment 2, the same subjects were tested in an Object guarding (OG) situation. A familiar woman, communicating the playful nature of the encounter, pretended to aim at taking away her belt-bag from the subjects trying to make them respond with guarding behaviour. Finally, she tried to take away the object without using dominant/threatening behaviour. During the Game episode some dogs and wolves showed guarding displays, but only dogs switched their responses twice and finally allowed the human take hold of the object. All dogs but none of the wolves gazed at the owner/caregiver during the test.

In Experiment 3, we tested trained Belgian shepherd dogs (N = 13) in AS, OG, and in a Food guarding (FG) situation. In FG a familiar woman challenged the subject to guard a bone by applying enticement but otherwise not communicating the playful/pretended nature of the encounter. Dogs displayed aggressive behaviours in all three situations as a response to the human's behaviour. In AS they adjusted their behaviour from passive/friendly to aggressive and then friendly again, according to the switch in the human partner's actions. In OG and FG situations, after showing aggressive guarding displays they allowed the human to take away the guarded object, both the bag and the food. A characteristic high-pitched vocalisation observed during both guarding situations, typically before the first aggressive display, could refer to the dogs’ ambivalent emotions. This suggests that the human's challenging behaviour alone might be effective to evoke a simulated guarding behaviour. Our results support the view that dogs have advanced abilities and readiness to combine seemingly contradicting behaviour responses to respond to human behaviours or expectations, whilst even hand-reared and extensively socialised wolves tend to display less human centred behaviours and adjust their behaviours less to that of humans’ in interspecific situations.