Chimps and Orangutans Hold on to Their Memories, Just Like Us

Scientists have discovered that chimpanzees and orangutans can use memory cues to remember things — very specific things — weeks to years later, much like humans do.

“There is good evidence challenging the idea that nonhuman animals are stuck in time,” according to Gema Martin-Ordas, a comparative psychologist at Aarhus University in Denmark. Her team conducted a first-of-is-kind study to determine if cues could cause apes to remember a past problem-solving event.

Martin-Ordas told io9 there are two types of long-term memory. Semantic memory is about the things we know — the facts we’ve learned as we’ve lived our lives. Episodic or “autobiographic” memories, on the other hand, are associated with a particular place and time and can be triggered by memory cues. That’s the type of memory we experience when, for example, a scent or a sound suddenly brings an experience from long ago flooding back.

Martin-Ordas and her team wondered whether orangutans and chimpanzees could join together a set of multiple cues they’ve seen only a few times — a process called “binding” and common to humans — to form a memory, and then recall that memory based on seeing those cues.

In a fascinating experiment, Martin-Ordas and her researchers worked with eight chimps and four orangutans at the Liepzig Zoo in Germany in 2009. Taking the apes individually, they showed each one a nice hunk of banana that was placed on a platform hooked to the exterior of a caged testing room. The banana piece could only be retrieved by using a long stick thrust through a slot.

While each ape watched, Martin-Ordas then hid two sticks in another room, only one of which was long enough to reach the banana. After observing all of this activity, the chimp or orangutan was then let loose into the room where the sticks were hidden. To get their treat, they needed to find the right sized stick, take it back to the area where the banana was waiting, and use the stick through the slot to snag the banana.

Martin-Ordas and the apes went through this scenario four times. She hid the sticks in different drawers each time, but the apes always got to see where they were put. They knew that only the longer stick would reach the banana.

Then time went by, during which many other behavorial experiments with Martin-Ordas came and went using the same set of rooms. Amazingly, in 2012 — three years later — 11 of the 12 apes remembered this particular experiment. When placed back into the same room with same researcher and the same banana on a platform, within 5 seconds they began searching the room for the longer stick so they could get their treat.

A set of seven control apes who hadn’t been exposed to the scenario didn’t search for any tool to get to the banana, even after five minutes in the room.

“I was really surprised that they could remember this event and they did it so fast,” Martin-Ordas told She said was testing the apes’ reaction to “a constellation of cues: me, the room, and the specific problem.”

The same apes could also remember a similar experiment two weeks after having seen it only one time. Researchers demonstrated how a ball placed on a see-saw sort of gadget would provide the user a frozen yogurt treat.

Martin-Ordas told the Los Angeles Times that two weeks later, “[i]nstead of showing them the whole event, when they came into the room we only showed them the task. And we used the task, and me, and the room, as the cues to see if we could trigger their memory.” Eleven of 12 apes remembered what to do and got their yogurt treat successfully. (The orangutan who forgot how the first experiment worked accomplished this one successfully, by the way).

Thanks to this research, we’ve learned something we never knew before about our primate cousins, the chimpanzee and the orangutan. Jonathon Crystal, a comparative psychologist at Indiana University, Bloomington told, “Three years is a remarkably long time to draw on a memory—not just for animals, but for us. It’s breathtaking.”

Think about these great apes and smile the next time you can’t remember where you put your car keys.

Related Stories:

Chimps More Like Us Than We Knew, Share Food With Each Other

Ape, All Too Human

Whales and Monkeys Learn Just Like We Do

Photo Credit: Thinkstock


Waheeda S.
Waheeda E4 years ago

Thanks for sharing. Makes me sad that these lovely animals are subjected to cruel tests by humans and then they remember it for such a long time. :(

Carrie-Anne Brown
Carrie-Anne B4 years ago

thanks for sharing :)

Manel Dias
Manel Dias4 years ago

With all the modern technology and the modern era facilities and equipments we no longer need to abuse animals for testing in laborataries. Those lab. practices were done in olden days when scientific findings were not that advance. This is a new era we live in. We do not need to abuse any animal in any laboratory doing such brutal experiments. Those so called scientists still insists they need to do experiments are THUGS. Such scientific laboratories are only functioning priliminarily to financially benefit while exploiting the animals. in the name of science.These aborataries are funded by the Tax payers money and the grants are in Millions of Dollars per annum. Need to listen to the modern era highly qualified scientists what they had to say on this subject too. Their final analysis is this so called laborotary test done on animals largely is a waste of tax payers dollar. Also mostly the animal testing does not truly help support human medical advancement. With the modern technology they need to do the human testings on the individual prior general administration of drugs. Then why these animals are being used at all? According to scientists what they said also if animals cannot be used to predict a human outcome in general then how can they be used to predict safety? Animals have the rights to live free from severe pain, sufferings & exploitations and there are no excuses not to.!!! Unless if there are exceptional & scientifically justified reasons...these animal

Melania Padilla
Melania Padilla4 years ago

Not surprising... It makes me so sad to think these beautiful animals can remember all of the abuses they go through because of humans ;(

Annelies Haussler
liessi Haussler4 years ago

It's about time people started waking up to this: animals are sentient as we are. Maybe they can't figure out the iPhone but that doesn't mean their lives, needs and emotions (yes, emotions!) aren't important. Now that we're starting to realize that their feelings and pain go far beyond nerve endings, I believe we're collectively (albeit slowly) starting to better understand our station in the natural order. And guess what? We ain't "all that."

Gita Sasi Dharan
Gita S4 years ago

Give them happy memories to cherish! Thank you for sharing.

KAREN L4 years ago


Donna Ferguson
Donna F4 years ago

I marvel at the abilities of animals. it makes me look at domesticated animals in a whole new way.

Esther Medina
Esther Medina4 years ago

It is not the scientific method that is in question here I believe. It is the headline and how it is written that makes most of us go "uh yeah duh". There is almost an "aha" feeling the headlines (care2 is not the only one) try to give us. So we just answer yeah, yeah I know.

I don't mean to make anyone feel badly, just explaining why I answered as I did. I believe we have a lot to thank the scientific method. As science gains knowledge the method also improves.

Jennifer Brooks
Jennifer Brooks4 years ago

This is a fascinating article. I would really love to email it to my friends, but EVERY time I try to email this article I get a completely different article instead. Is this Care2's new policy: to send the customer every single article on the website except the one they ASKED FOR?