Chimpanzees and orangutans have long term memories too

image The Telegraph

Interesting work in a new paper is published in Current Biology. It supports my view that life is a continuum from simple to complex with no place for – or any need to invoke – a “soul”. At what point the brain of a species is large enough and complex enough not only to be able to “save” memories but also to then access these data at a later time is also unknown. I have little doubt from the  dogs and cats that I have known that they can “remember” people and behaviour from many years before  – even if they are often  supposed to live only in the “now”. At what point in this continuum “self-awareness” emerges is not known but I suspect that it depends on the definition of “self-awareness” and some level of self-awareness lies very close to the “simple” end of the scale of life.

(Certainly the mosquito which got trapped in my study yesterday was not just “self-aware”, it was also maliciously aware of me. If it had a soul it has now been consigned to mosquito hell!!)

This work shows that chimpanzees and orangutans have the ability to “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” 

Gema Martin-Ordas, Dorthe Berntsen, Josep Call. Memory for Distant Past Events in Chimpanzees and OrangutansCurrent Biology, 2013; DOI: 10.1016/j.cub.2013.06.017


  • First study addressing unexpected and cued recall of both general and unique events
  • Chimpanzees and orangutans recalled events that happened weeks and years earlier
  • Subjects also showed evidence of binding
  • Chimpanzees and orangutans share this form of autobiographical memory with humans


Determining the memory systems that support nonhuman animals’ capacity to remember distant past events is currently the focus an intense research effort and a lively debate. Comparative psychology has largely adopted Tulving’s framework by focusing on whether animals remember what-where-when something happened (i.e., episodic-like memory). However, apes have also been reported to recall other episodic components after single-trial exposures. Using a new experimental paradigm we show that chimpanzees and orangutans recalled a tool-finding event that happened four times 3 years earlier (experiment 1) and a tool-finding unique event that happened once 2 weeks earlier (experiment 2). Subjects were able to distinguish these events from other tool-finding events, which indicates binding of relevant temporal-spatial components. Like in human involuntary autobiographical memory, a cued, associative retrieval process triggered apes’ memories: when presented with a particular setup, subjects instantaneously remembered not only where to search for the tools (experiment 1), but also the location of the tool seen only once (experiment 2). The complex nature of the events retrieved, the unexpected and fast retrieval, the long retention intervals involved, and the detection of binding strongly suggest that chimpanzees and orangutans’ memories for past events mirror some of the features of human autobiographical memory.

From Science Daily:

…. “Our data and other emerging evidence keep challenging the idea of non-human animals being stuck in time,” says Gema Martin-Ordas of Aarhus University in Denmark. “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.” ….. 

“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 says. “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.”

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