Chimpanzees and orangutans were able to remember things from years past if given sensory reminders.
In the study chimps were presented with two boxes, each in a different room. One contained a useful tool while the other contained a meaningless object, the BBC reported.
The chimps were rewarded if they were able to retrieve the more favorable tool. Three years later they were still able to retrieve figure out where the right one was.
It's well known that sensory information, like the smell of your mom's pancakes, can help bring back memories. The Aarhus University team used the same principle for testing the primates' memory. About 90 percent of the primates were able to locate the correct tool as long as the boxes were set up in the exact same way they had been three years prior.
"Our data, and other emerging evidence, keep challenging the idea of non-human animals being stuck in time," Dr. Gema Martin-Ordas, who led the study, said.
The experiment showed chimpanzees were able to recall events from up to three years earlier, even if they were not trained or expecting to have to remember the information.
"What this shows is that the episodic memory system in humans is not as unique as we thought it was, as we share features with non-human primates," Martin-Ordas said.
The findings could mean the ability to create memories is older than mankind.
"I think it's important to know who we are and what makes us unique. Learning about what other species can do gives us a more comprehensive picture about humans," Martin-Ordas said.
Michael Corballis from the University of Auckland, who was not involved with the study, believes primates are closer to humans than we give them credit for. The difference between human and primate memories was the chimps were not able to remember when an event happened.
"There is no indication that the animals remembered when the earlier event occurred. This is not to say the animals had no inkling of this, and in any case we humans are often hazy about the locations of events in time." Corballis said. "My guess is that great apes, and perhaps even rats, have episodic memories similar to our own, probably less rich and detailed, but similar in essence."
