Scientists at Aarhus University say in laboratory tests both primate species were clearly able to recollect a tool-finding event that they had experienced just four times 3 years earlier and a singular event from two weeks before.
"Our data and other emerging evidence keep challenging the idea of non-human animals being stuck in time," researcher Gema Martin-Ordas said.
"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."
Reporting in the journal Current Biology, the researches said the chimpanzees and orangutans in the study could also distinguish between similar past events in which the same tasks, locations, and people were involved.
"This is a crucial finding since it implies that our subjects were able to bind the different elements of very similar events -- including task, tool, experimenter," Martin-Ordas said. "This idea of 'binding' has been considered to be a crucial component of autobiographical memories."