Pet dogs’ Behavioural Reaction to Their Caregiver’s Interactions with a Third Party: Join in or Interrupt?

SIMPLE SUMMARY: Behavioural studies in dogs have shown that dogs form strong bonds with their caregivers and display attachment behaviours towards them, especially in stressful situations. Some observational studies in dogs and dog caregivers frequently reported the occurrence of jealousy-like behaviours, particularly during affiliative caregivers’ interactions with other dogs; so-called social rivals. Thus far, due to contradictory results, this phenomenon remains unclear. In this study, we investigated pet dogs’ behavioural reactions during two different types of interactions (greeting vs. examining) performed either by the dog’s caregiver or a stranger with a remotely controlled, realistic-looking fake dog. We predicted that the dogs would rather respond in a jealousy-consistent manner when observing their caregiver interacting in an affiliative way with the fake dog. During the tests, the dogs observed the interaction at first and could later join in. We found that the dogs’ initial neutral or negative reaction towards the fake dog changed to a more positive reaction during the affiliative interaction of the caregiver with the fake dog. When joining in with the interaction, more dogs displayed friendly behaviours towards the fake dog when the caregiver was present, but they also tried to block the interaction more often, as compared to the stranger–fake dog interaction. Taken together, we did not observe clear jealousy-like behaviours in the dogs but found indicators of social referencing and behavioural synchronization of the dogs with their caregivers which supports the assumption that human affiliative behaviours towards others can facilitate dogs’ positive reactions. ABSTRACT: Pet dogs are promising candidates to study attachment-related and potentially jealousy-like behaviours in non-human animals, as they form a strong and stable bond with their human caregivers who often engage in affiliative interactions with diverse social partners. Nevertheless, it is still debated whether non-human animals are capable of experiencing such complex emotions. Even though caregivers frequently report observations of jealousy-like behaviours in dogs, behavioural studies in dogs have thus far led to contradictory results. Adding to this complexity, dogs appear extraordinarily skilled in understanding humans’ communicative behaviour and can flexibly and diversely interact with them in social contexts. Here, we aimed at investigating (1) whether dogs indeed respond in a jealousy-consistent manner when seeing their caregiver interact in an affiliative way with a remotely controlled, realistic-looking fake dog, or (2) whether they would rather synchronize their reaction to the fake dog with the caregiver’s behaviour, or (3) whether they respond directly to the caregiver without paying much attention to the third party. To address what drives the dogs’ behaviours in this triadic situation, we compared four groups of dogs who first observed and then joined the interaction of either the caregiver or a stranger greeting or medically examining the fake dog. We found that the dogs initially responded negatively or neutrally when the fake dog entered the room but changed to more positive reactions when the caregiver approached the fake dog, especially if initiating a positive interaction. When being released, more dogs showed friendly behaviours towards the fake dog when the caregiver—rather than the stranger—was interacting with it. At the same time, however, the dogs tried to block the interaction of the caregiver with the fake dog more often than the one of the stranger. In conclusion, we did not find clear evidence for jealousy-like behaviours in dogs during the human–fake dog interactions, but we observed indicators of behavioural synchronization with the caregivers, suggesting that the caregivers’ affiliative behaviours directed at a third party may more often facilitate positive than negative interactions in dogs.