Food has long been the currency of the 10,000-year-old friendship between humans and dogs. The rapport started with our ancestors sharing food with wolves, and today, we show our love to our canine pets with treats and train them with goodies as motivation. However close the bond is between humans and dogs, though, food sharing may just be a one-way street: Dogs don’t seem to pay back the hand that feeds them.
That lack of reciprocated food sharing in dogs is the key finding of a study published today in PLOS One by dog researcher Jim McGetrick and his team. The comparative psychologist at the University of Veterinary Medicine, Vienna in Austria found that in lab experiments, dogs who received treats by humans pushing a button didn’t then return the favor by pushing the same button so humans gained a treat in kind.
“In terms of dog domestication and the evolution of dogs as a species, their cooperativeness with humans might not be related to this form of cooperation: this reciprocal cooperation, where I help you and then you help me at some point in the future,” says McGetrick.
Previous studies have observed that dogs repay other generous dogs with food tit-for-tat, and take the initiative to rescue distressed humans from entrapment. McGetrick says his study is the first to look at reciprocity between humans and dogs. His team wondered whether fed dogs would reward food to beneficent humans.
To probe this question, the researchers trained 37 pet dogs to press a button for food from a dispenser. These dogs came from over ten different breeds and mixes, with diverse idiosyncrasies to match. Some dogs were gentle, laying their paws delicately on the button and nibbling their reward. Other dogs mauled the button and chewed on the box that enclosed it. One dog only pressed the button with its hind leg.
“The personalities definitely varied hugely,” says McGetrick.
Once each dog associated the button with food, the button was placed in an adjacent room with a human stranger inside. The dog would remain in a different room with the food dispenser. A wire mesh fence separated the two rooms—through which the dog could observe the human controlling the coveted button. A helpful human would press the button and the dog would receive food. An unhelpful human would steel his or her heart against the dog’s pleading eyes—unbeknownst to the dog, the volunteer usually felt terrible—and press a decoy button that didn’t release any food from the dispenser.
“When they were with the unhelpful human, it surprised me how big of a deal it was for them when they didn't get food in a situation where they expected to get food,” says McGetrick. These dogs whined and made a fuss. “It could look effectively like throwing a tantrum.”
The researchers then reversed the situations. The working button was transferred to the room with the dog, and the food dispenser—with chocolate candy replacing the kibble—was relocated to the human’s room. This time, the dogs weren’t nearly so eager to press the button in their room when the food ended up with the human next door. Moreover, when it came to reciprocating the helpful human who had previously fed the dog via the button or the unhelpful one who had refused, the dogs didn’t seem to distinguish between the two. The dogs pushed the button equally for both groups.
Moreover, after each button-pressing experiment, the dogs and humans had the chance to interact in the flesh. The dogs didn’t seem to hold the volunteers’ unhelpfulness against them. They approached the volunteers equally, whether the humans had been helpful or not.
“[The result] could indicate that dogs might not necessarily … relate to something like gratitude,” says McGetrick. Or, “they don't necessarily strongly regard or consider others in their actions” in an attentionally blind kind of way, he adds. But “I would highlight that this was a very specific experimental context.”
The findings don’t necessarily rule out reciprocity by dogs with humans, says McGetrick. The experimental outcome could be specific to the conditions that the researchers used, such as the dogs’ unfamiliarity with the humans. Perhaps the dogs would be more helpful in kind to their original owners. Or, button-pushing was too much of a mental leap for the dogs to associate with returning the favor. He suspects that the dogs may go by a more straightforward rule: push the button only when the dispenser is in their room. More likely, he speculates, dogs simply don’t see themselves as food providers to humans. What humans have going on with dogs is more of a master-servant relationship, rather than two partners on equal footing.
“The key thing is, are we asking the question in the right way that the animals understand?” says Jeffrey Stevens, a psychology researcher at the University of Nebraska-Lincoln who wasn’t involved in the study. “Dogs in particular, they have a completely different world than we do right there.” For example, dogs perceive their environment mainly with their sense of smell rather than their sight. Experiments should be designed from the perspective of the dog, not the human, such that the pooch can easily recognize the task at paw. “You want to make sure that you've really tried to set up a situation where the animals have the best opportunity to demonstrate their abilities.”
More research is needed to rule out all the possibilities that could explain why the dogs didn’t reciprocate with food, says Angie Johnston, a psychology researcher at Boston College who didn’t participate in the research. A good starting point would be to look at dogs who have received more training, such as military and service dogs. If even trained dogs don’t keep score, it would imply dogs in general are hopeless at tracking this information. But if they reciprocate, then training might make all the difference, allowing any canine to pay more attention to the humans they work with.
“Knowing about the dog-human interaction is important for things like training service dogs and assistance dogs,” says Johnston. “Anytime we know more about the human-dog connection and where it came from and how it evolved, that can inform our training processes with those populations.”