Study finds evidence that dogs have episodic memory
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.
Humans have episodic memory, and that's pretty easy to prove, because we can use our words to describe the past events we recall. Demonstrating that animals have it is much 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 remember them.
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 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!”
“We cannot directly investigate what is in the dog's mind,” said lead author Claudia Fugazza, an ethologist at the University of Eotvos Lorand in Budapest. “So we have to find behavioral evidence of what they expect or not.”
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 in an email. “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.”
Fugazza and colleagues had previously carried out a variation on this study that didn't involve messing with the dogs' expectations. In that one, the dogs were not taught to lie down, but just to “Do it!” — which the researchers say means the dogs expected to be told to imitate. The canine participants in that study aced that test, with 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.