She and her colleagues challenged their canines to a simple task, which other scientists have used on all kinds of brainy animals — chimps, monkeys, parrots, ravens, and even elephants. There’s a food-bearing tray that lies on the other side of their cage, tempting and inaccessible. A string is threaded through rings on the tray, and both of its ends lie within reach of the animals. If an individual grabs an end and pulls, it would just yank the string out and end up with a mouthful of fibers — not food. But if two animals pull on the ends together, the tray slides close, and they get to eat.
All in all, the dogs did terribly. Just one out of eight pairs managed to pull the tray across, and only once out of dozens of trials. By contrast, five out of seven wolf pairs succeeded, on anywhere between 3 and 56 percent of their attempts. Even after the team trained the animals, the dogs still failed, and the wolves still outshone them. “We imagined that we would find some differences but we didn’t expect them to be quite so strong,” Marshall-Pescini says.
It’s not that the dogs were uninterested: They explored the strings as frequently as the wolves did. But the wolves would explore the apparatus together — biting, pawing, scratching, and eventually pulling on it. The dogs did not. They tolerated each other’s presence, but they were much less likely to engage with the task at the same time, which is why they almost never succeeded.
“The dogs are really trying to avoid conflict over what they see as a resource,” says Marshall-Pescini. “This is what we found in food-sharing studies, where the dominant animal would take the food and the subordinate wouldn’t even try to approach. With wolves, there’s a lot of arguing and it sounds aggressive, but they end up sharing. They have really different strategies in situations of potential conflict. [With the dogs], you see that if you avoid the other individual, you avoid conflict, but you can’t cooperate either.”
“Amazingly, no one had ever studied whether carnivores could solve this type of cooperative task, and it’s fun to see that the wolves coordinated,” says Brian Hare from Duke University, who studies dog behavior and the influence of domestication. He has argued that during the domestication process, dogs began using their traditional inherited mental skills with a new social partner: humans.
Simultaneously, dogs perhaps became less attentive to each other, adds Marshall-Pescini. After all, wolves need to work together to kill large prey, and sharing food helps to keep their social bonds intact. But when they started scavenging on human refuse, they could feed themselves on smaller portions by working alone. If they encountered another forager, “maybe the best strategy was to continue searching rather than to get into conflict with another dog,” she says.
But dogs can be trained. When owners raise dogs in the same household, and train them not to fight over resources, the animals start to tolerate each other, and unlock their ancient wolflike skills. This might be why, in 2014, Ljerka Ostojic, from the University of Cambridge, found that pet dogs, which had been trained in search and rescue, had no trouble with the string-pulling task that flummoxed Marshall-Pescini’s dogs.
“It speaks to the fact that living among other dogs, without interaction with humans, is arguably less natural for dogs — as if domestication both refined attention, coordination, and even pro-sociality between species, and weakened social skills within the species,” says Alexandra Horowitz, who studies dog cognition at Barnard College. “A pack of dogs living together, without human intervention, is impaired compared to dogs living with humans.”