Jealousy is a fairly common human emotion — and for a long time, it was presumed it truly was only human. Some have argued that jealousy, with its focus on social threat, requires a concept of “self” and a theory of mind — being jealous of someone flirting with your partner, for example, requires a level of threat (real or imagined) to your relationship. This element of jealousy has been used to argue that animals, without such a sense of self, are therefore unable to experience it.
However a new study, published in Psychological Science, suggests this might not be the case. Amalia P. M. Bastos and team from the University of Auckland find evidence that dogs may, in fact, be able to mentally represent the threatening social interactions that give rise to jealousy.
Some previous research has already suggested that dogs get jealous — one 2018 study, for example, found that dogs would move in between or push owners away from interactions with fake dogs. But that research didn’t provide conclusive evidence that the dogs were actually experiencing jealousy.
In the new study, the team recruited 18 dogs and their owners: all dogs had been in the household for at least six months, were non-aggressive and showed no signs of discomfort within the experimental setting, removing the possibility that they would move towards a fake dog out of aggression or fear.
The owner sat behind a large barrier, wearing a blindfold and noise-cancelling headphones. The dogs were placed around five metres away, tied to a door frame attached to a force gauge in order to measure how hard they pulled on their leash.
In the fake dog condition, a realistic-looking fake dog was placed next to the owner behind the barrier. The barrier was then moved across the room for five seconds in order to reveal the fake dog to the real dog. When the barrier was moved back, blocking the view of the fake dog, the owner was instructed to pet and talk to it as if it were real.
In the cylinder condition, on the other hand, owners were shown petting and talking to a fleece cylinder behind the barrier. The realistic looking fake dog was still in the room, however, placed behind a separate, smaller barrier and revealed to the real dog.
Dogs in the fake dog condition pulled significantly harder on their leashes than those in the fleece cylinder condition, suggesting that the dogs were attempting to break up the interaction between their owner and a perceived rival. The fact that the fake dog was present during the cylinder trials is important, showing that the mere presence of a rival wasn’t enough to invoke jealous behaviours: it was the actual interaction with the dog’s owner that led to increased jealous behaviour. When the dogs were later allowed to reach the fake dog, the team also found that the dogs engaged in genital and face sniffing — suggesting that they believed the fake dogs were real throughout the study.
Overall, the dogs seemed to show “signatures” of jealous behaviour similar to those in humans: they reacted to a social partner engaging with a social rival (the fake dog) but not another object (the fleece cylinder), and didn’t react when the rival was in the room but not engaging with their owner. And most strikingly, they reacted strongly even though they couldn’t directly see the interaction between the owner and rival. Together, this suggests that dogs do indeed experience some form of jealousy, and can even mentally represent the social interactions that give rise to jealous feelings.
This insight is important for several reasons, not only confirming previous research on jealousy in dogs but suggesting that dogs may have more complex cognitive abilities than we might assume. This may indicate the ability to conjure other mental representations in different situations — and a much richer inner life than we currently understand.