Researchers found that both primate species were able to recall where to search for tools and the location of a tool both two weeks and three years after initially doing so.
The findings show that people and their primate cousins have more in common in terms of memory than previously believed, according to the authors of the study published July 18 in the journal Current Biology.
"Our data and other emerging evidence keep challenging the idea of non-human animals being stuck in time," Gema Martin-Ordas, of Aarhus University in Denmark, said in a journal news release. "We show not only that chimpanzees and orangutans remember events that happened two weeks or three years ago, but also that they can remember them even when they are not expecting to have to recall those events at a later time."
The researchers were impressed by the complexity and speed of the recall ability shown by the chimps and orangutans.
"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 said. "On average it took them five seconds to go and find the tools. Again, this is very telling because it shows that they were not just walking around the rooms and suddenly saw the boxes and searched for the tools inside them. More probably, it was the recalled event that enabled them to find the tools directly."
These findings mark the start of a completely new line of research on memories for past events in animals, she said.
NASA has more about human memory.