Monkey memory
Capuchin monkeys have an integrated memory with characteristics similar to humans Charles Janson

Just like humans, capuchin monkeys may possess integrated, episodic memories – an ability to recall prior knowledge to inform behaviours in new situations. A scientist has shown that the little primates were able to remember where food patches were hidden relative to their current location, how productive patches were and more surprising, how long it had been since they last visited the patch.

One of the most important characteristics of human intelligence is that they have a very developed, integrated memory. Humans are able to remember past event with a lot of context-specific details, an ability which was thought to be specific to the species.

However, a number of studies have recently hinted that some animals held in captivity also have similar memories of past events, with a recollection of what happened, where and when.

This latest study, published in the Proceedings of the Royal Society B, is based on previous experiments conducted in Argentina with capuchin monkeys which revealed that the animals could recall both the location and amount of food at patches they had previously visited.

Deciding which feeding site to visit

Here, author Charles Janson, from the University of Montana, tested whether capuchins also made their decisions of which feeding patch to go to based on the amount of time that had passed since their last visit.

He introduced the monkeys to eight feeding sites. At each site, food rewards increased in quantity with increasing elapsed time since the previous visit – a pattern which mimicked the phenomenon of ripe fruit accumulation in trees. During 68 days, a group of monkeys repeatedly visited the sites, while Janson observed them.

Using statistical models, the researcher was then able to make a sense out of his observations, finding out that the monkeys followed a certain logic in their choices of sites – a logic which was consistent with remembering when they had made a previous visit to a particular site. On average, the animals would choose the site which they anticipated to have the largest quantity of food. They would often let some time go by before returning to the same place, in order to get more food.

"It appears that capuchin monkeys possess and use integrated memories of prior food patch use, including where the patch is relative to their current location, how productive the patch is and how long it has been since they last visited the patch", Jansen concludes. Human intelligence may thus have characteristics in common with intelligence in other primates.