Plants and Animals

Monkeys Can Rate The Reliability Of Their Memories

We’ve all been there, thinking we can remember something but not really sure if it’s safe to trust those memories. This level of awareness of our brain’s unreliability seems like a uniquely human attribute, part of our awareness of who we are. Yet in a stunning finding for animal consciousness, it turns out macaques have it too.

A team led by Dr Kentaro Miyamoto of the University of Tokyo had two Japanese macaques (Macaca fuscata) perform visual memory recognition tests indicating whether they had previously seen an image of an object.

Once both monkeys had performed the task thousands of times and understood what was being asked of them, they were given a chance to make either a low or high value bet on their most recent answer being right. This tested their awareness of whether their memories are reliable or not by demonstrating their confidence in whether they really had seen an image before.

In a paper published in Science, Miyamoto reports that the macaques found the initial test hard, getting it right only a little more than would be expected by chance. Nevertheless, over a period of five months, they came to understand the two-stage process. Low value bets, indicating a lack of confidence turned out to have been right almost exactly 50 percent of the time. On the other hand, the monkeys scored over 60 percent when they had placed high value bets.

Although the difference is not large, the tests were done often enough to easily achieve statistical significance. In the process, they demonstrated that these non-humans possess a true awareness of the possibility that their memory is playing tricks on them, and some capacity to assess when they were right.

The monkeys also took longer to provide wrong answers than those that were correct, the hesitation indicating a lack of confidence.

The findings, besides proving once again that our primate brethren are smarter than we think, gives us a chance to learn about metamemory, the capacity to monitor our memory state and evaluate these memories. It is one of the many advanced capacities of the brain we don’t really understand – we don’t even know where in the brain it takes place, unlike memory itself, which has been accurately placed.

Miyamoto’s work may help change this situation. Some trials were conducted in functional Magnetic Resonance Imaging (fMRI) machines, allowing identification of areas of the macaque brain that were differently active when placing high and low value bets. When the monkeys were confident enough in their memories to be willing to place larger bets additional activity was seen in specific areas of the prefrontal cortex of the brain. Whether this area performs the same role in humans needs further investigation.

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