Chimpanzees and orangutans can remember events that happened years ago, according to a recent study. New evidence suggests their long-term memories can be triggered by unique flavors or scents.
In a study published Thursday in Current Biology, both primate species remembered how to find tools to help them find bananas or frozen yogurt -- something they had learned three years earlier and had only performed four times, the Los Angeles Times reports.
"Our data and other emerging evidence keep challenging the idea of nonhuman animals being stuck in time," comparative psychologist Gema Martin-Ordas, of Aarhus University in Denmark, said in a statement.
In lab experiments, scientists studied 15 chimpanzees and four orangutans and tested their ability to remember events that happened years ago. In one test, the researchers asked the primates to recall an experiment conducted three years ago. At the time, researchers hid tools needed to find rewards. In the latest experiment, researchers brought the primates to the same room to see if the chimps remembered where the tools were hidden.
The primates passed the test with flying colors. "I was surprised to find out not only that they remembered the event that took place three years ago, but also that they did it so fast,” Martin-Ordas told LiveScience. "On average, it took them five seconds to go and find the tools."
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Martin-Ordas credits the chimps’ quickness to their memory. The fact that they weren’t wandering around the room testing to see where the tools were led scientists to the conclusion they were remembering a past event.
Another test involved another tool-finding mission with a different setup, which the chimpanzees were asked to repeat two weeks later. Again, scientists observed the animals correctly recall where to look.
“You can’t really ask a chimpanzee,” Martin-Ordas told the Los Angeles Times about the challenges surrounding the study. “The only thing we can do is accumulate pieces of evidence and see how close we can get to the idea of autobiographical memory or episodic memory without showing conscious recollection.”