The ability of rhesus macaques to draw shapes from memory suggests that monkeys may have as-yet-unexplored powers of recall, possibly similar in some ways to human recollection.

In earlier studies, macaques have recognized previously-seen objects. Psychologists consider recall to involve different cognitive capacities than recognition, which seems to use different parts of the brain and is arguably less demanding. Recognition is just a matching task, but recall hints at a richer life of the mind.

“The question that was driving us was, ‘How would you know if an animal was thinking about or remembering something that wasn’t there?’” said psychologist Benjamin Basile of Emory University. “The difference between recall and recognition is really critical.”

In a study published April 28 in Current Biology, Basile and Emory psychologist Robert Hampton showed five rhesus macaques simple figures on a computer touch screen, then displayed the figures in a partial form that the monkeys drew to complete.

The monkeys passed the test. If their monkeys’ capabilities are replicated in other labs, researchers can begin to investigate the phenomenon in greater detail.

“Whether monkeys sit there and recollect the past, we don’t know. What we believe we found in these lab studies is that they can recollect simple information, over short time periods,” said Basile. “Whether they use it in their daily lives, we don’t know. These are fascinating questions.”

The questions lead towards what monkeys think and feel — something that can’t be completely quantified with current methodologies, and some researchers argue that long-term field observations of monkeys are undervalued in comparison to their performance on human-designed lab tests.

But those tests are the benchmarks of cognitive science, and monkey cognition is an intellectually compelling subject of inquiry. With more than 100,000 monkeys currently housed in U.S. laboratories, it’s also ethically compelling.

An open question is whether, and to what degree, monkeys might possess what psychologists call a “theory of mind,” or the ability to think about thinking, and to ascribe mental states and feelings to other creatures.

Chimpanzees are considered by some researchers to possess something like a theory of mind, but cognition in macaques is considered less advanced. However, some studies suggest that macaques may demonstrate conscious intent, understand the differences between their own experiences and those of others, and recognize themselves in mirrors — all of which are pieces of a theory of mind. So, too, is recall.

“How complex can their recall performance be? We don’t really know. It’s certainly possible they do something similar to what we do when recalling information, but not as complex or long-lasting,” said Basile.

Ronald Green, a bioethicist at Dartmouth University, cautioned against over-interpreting such studies. Just because animals demonstrate a series of mental capacities doesn’t mean they’re persons, at least not in the way humans define the concept.

Such findings do, however, underscore the importance of our obligations to monkeys in research, he said.

“It’s a mistake to jump from some capacities to the claim of moral beings,” said Green. “We’re the moral beings — and understanding that means we have to make judgments about the use of animals in research environments.”

Video: A rhesus macaque completes the recall test. (Benjamin Basile)
Photo by Jinterwas/Flickr.

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Citation: “Monkeys Recall and Reproduce Simple Shapes from Memory.” By Benjamin M. Basile and Robert R. Hampton. Current Biology, April 28, 2011.