Think back to what you ate for breakfast this morning. Did you picture yourself in your kitchen and visualize the plate in front of you to remember exactly what you ate?
That's called an episodic memory – a memory of a particular event that happened at a specific time and place, as opposed to a semantic memory, which refers to more general knowledge or rules that someone understands.
Cognitive scientists have long thought that humans were the only animals capable of traveling down memory lane by having episodic memories. Dogs, for example, were known to commit things to semantic memory. When repeatedly trained to sit, stay, or lie down, they learn a rule. But they, like other nonhuman animals, were thought to live exclusively in the here and now – until now.
It turns out Fido can remember specific events too.
Every dog owner knows their beloved canine is the smartest dog in the world, and of course she remembers that amazing fall hike you took together last weekend. But now scientists have found evidence that dogs can experience episodic-like memories, adding to a growing understanding of animal intelligence – and potentially offering new insights into how to train your dog.
This research comes at a time when scientific studies are revealing just how complex cognition might be across the whole animal kingdom. In just the past year researchers have found evidence that ravens possess a theory of mind, great apes can see things from perspectives other than their own, and ducklings might be capable of abstract thought.
"Dogs remember events around them, even when the events are quite complex and context-rich," Claudia Fugazza, an ethologist at Eötvös Loránd University in Hungary, says in a phone interview with The Christian Science Monitor.
"They may recall things that they just witness or experience even though they do not seem to be important," she says. "They may remember what the owner does, not only when the owner prepares the food for the dog, but also when the owner does other things that might seem less relevant for the dog, dogs may still encode this and remember."
Dr. Fugazza and her colleagues tested dogs' memories by asking them to replicate a random action performed by their owner when they weren't expecting to imitate the action in a study described in a paper published Wednesday in the journal Current Biology.
The dogs selected for this study had already been trained in the "Do as I Do" imitation behavior in which dogs had been trained to imitate their owner's random behavior. For example, an owner spins in a circle and then says "Do it" and the dog spins in a circle. The dog may have never spun in a circle before, but it has learned to imitate its owner.
But direct mimicry wouldn't help the researchers test the dogs for episodic-like memory. They had to make sure the imitation test was unexpected for the pooches, so they didn't know to commit a random action to semantic memory as a rule. So the dogs were then trained to perform a simple exercise: to lie down. The intention was for the dogs to expect to be told to lie down, not to imitate a random action by the owner.
The actual memory test went like this: the owner would perform a random action, like hitting an open umbrella. Then, when the dog was expecting the "Lie Down" command and would lie down as such, the owner would surprise them by saying "Do it." Researchers found that the dog would then walk up and touch the umbrella with its paw – an action it had never done and hadn't been told to remember, but had watched the owner do.
The test was run at two intervals: the "Do it" command was given one minute and one hour after the owner had performed the action.
And, like humans, the dogs are able to remember the event, even if it doesn't seem important at the moment, Fugazza says. But, also like humans, the more time has elapsed since the event, the worse the dogs' memories seem to be.
"I think it makes sense because you do not know you are supposed to remember this information, so you may forget it sooner," she says.
In the minds-eye of an animal
Many cognitive scientists have long thought that humans were the only animals capable of having vivid memories of specific events – or episodic memories. But evidence is mounting against that.
Previous studies of other animals, including pigeons and rats and apes, have suggested that nonhuman animals are capable of at least episodic-like memory. For example, rats have been able to indicate whether or not they were fed earlier. Or jays have been observed returning to food that they have buried, presumably remembering the location thanks to an episodic-like memory.
But, as Brian Hare, an evolutionary anthropologist who founded the Duke Canine Cognition Center at Duke University but was not involved in the research, points out, those would be details that would be particularly significant for the animals to remember to survive. "Here, dogs copping arbitrary actions, touching umbrellas with their paw, it's meaningless," he says in a phone interview with the Monitor.
Not only that, but the dogs aren't even remembering actions that they themselves have done. And, with the delay before being asked to imitate, "I think it removes certain possible confounds, like muscle memory," Thomas Zentall, a psychologist studying the cognitive behaviors of animals at the University of Kentucky who also was not involved in the research, says in a phone interview with the Monitor.
"I think it's quite impressive," he says. "It suggests that the animal has to, in a sense, think back to a representation that it has, recreating a past event in its mind."
Laurie Santos, a psychologist studying comparative cognition at Yale University who was not involved in the study, agrees that the research is "clever," but she adds that there are remaining questions about what the dogs actually remember about their owners' actions. "For example, do dogs really experience this event as a specific episode involving a particular person at a particular place," she writes in an email to the Monitor. "Do dogs' memories have the "who, what, where, when" quality of human memories. I think the current research is an excellent first step, but that it only opens new questions concerning the richness of dogs' memories."
Dr. Zentall isn't so sure that the "who, what, where, when" of an event are the best criteria to determine if an animal is capable of episodic memories. He points out that humans can experience vivid memories without the precise when or even where. Instead, he suggests, it might have to do more with being able to recreate and visualize a past event in one's mind.
But, of course, it's difficult to figure out what sort of snapshots exist in the minds of animals that do not share language with humans, Fugazza points out.
Does this mean dogs have a sense of self?
One of the reasons there has been a debate around whether or not nonhuman animals can possess episodic memory is because it is traditionally linked to self-awareness, Fugazza explains. "So far it is not known whether dogs possess this cognitive ability or not, so that's why we call it episodic-like memory" in the new study, she says.
Dogs have not passed the classic self-recognition test of whether they can recognize themselves in a mirror. Dr. Hare even wrote in his 2013 book "The Genius of Dogs: How Dogs Are Smarter than You Think" that there was no evidence that dogs have self-awareness. But, he says after reading Fugazza's new paper, "I can't say that anymore … This certainly reopens the question."
At minimum, Hare says, this research could change how humans currently train dogs. "The way that most people think about how dogs learn is that it really is about practice and reward. And it requires a lot of elbow grease and repetition," he says. But perhaps if people can better understand how dogs learn, "we're going to be able to teach our dogs much faster and in a much more humane way than currently I think is the norm."