Do you remember what you did last year on Thanksgiving? If so, that’s your episodic memory at work — you’re remembering an experience that happened at a particular time, in a particular place, maybe with particular people, and probably involving particular emotions.
It’s pretty easy to prove humans have episodic memory, because we can describe past events we recall. Demonstrating that animals have it is more difficult.
But now researchers in Hungary say they’ve found evidence that dogs have episodic-like memory (they added the “like” because they acknowledge they cannot get inside a dog’s head to absolutely confirm this), specifically when it comes to remembering what their owners do. Even more interesting is that they can remember these things even when they don’t know they’ll have to.
To determine this, the researchers put 17 pet dogs through a multistep training process designed to first make them memorize an action, then trick them into thinking they wouldn’t need to do it. The dogs’ performance was described in a study published Wednesday in Current Biology.
First the dogs were trained in what is known as the “do as I do” method. It involves a dog’s owner demonstrating an action — say, touching a traffic cone or an umbrella — and then telling the dog to “Do it!” The pups’ successful imitations were rewarded by treats. Once they had mastered that trick, the owners switched things up on them. They performed an action, but instead of asking the dogs to imitate it, the humans told the pets to lie down. After several rounds of that, all the dogs eventually were lying down spontaneously — a sign, the authors wrote, that they’d lost any expectation that they were going to be told to imitate, or “Do it!”
Next, the owners switched things up on the dogs yet again. They’d do the action, and the dogs would lie down, and then the humans would totally violate the poor pooches’ expectations by waiting one minute and saying, “Do it!” The owners made the same command after waiting an interval of one hour.
This was the test: Had the dogs tucked the memory of their owners’ actions somewhere in their mind, and could they dig it out?
After the one-minute interval, about 60 percent of the dogs imitated the human action, even though they probably didn’t expect to be asked to. After the one-hour wait, about 35 percent imitated the action.
“What’s lovely about the study is the way it shows dogs remembering an action that they’d seen at a later time — without doing it themselves,” Alexandra Horowitz, who runs the Dog Cognition Lab at Barnard, wrote. “It speaks to what might be on their mind: that they are remembering episodes that they witness, not just things that they are the subjects of.”
Lead author Claudia Fugazza, an ethologist at the University of Eotvos Lorand in Budapest, and colleagues had previously done a variation on this study without messing with the dogs’ expectations. Those dogs were not taught to lie down, but just to “Do it!” — which the researchers say means they expected to be told to imitate. The canine participants aced that test, nearly all imitating the human actions even after a one-hour delay.
The dogs’ much lower success in the current study “also suggests they were really using their episodic-like memory, because episodic memory in humans is known to decay faster, too,” Fugazza said.
Horowitz said she was perplexed, though, by the fact that more than one-third of the dogs studied didn’t imitate even after just one minute. “We wouldn’t expect some dogs to remember past events and others not,” if episodic-like memory is an ability that can be generalized to a species, she said.
Clive Wynne, a behavioral scientist who directs the Canine Science Collaboratory at Arizona State University, also expressed doubt that the results clearly demonstrated episodic memory, or something like it, in dogs.
“Maybe a lot of experience of “Do it” has led the dogs to always pay at least some attention to what the human does in case they are asked to copy it,” he said. “I can think of lots of not very exciting explanations for these findings.”
The authors say the results are the first demonstration of nonhumans’ remembering complex events without practicing them. Fugazza said she thinks the study also shows dogs are more like us than we might believe.
“I think every dog owner knows that dogs remember events. What is new and important is that dogs can remember events even if those events do not seem to be important,” she said.
“Dogs probably pay more attention to us than we think and observe us more than we think,” Fugazza added.
