EMORY (US) — Monkeys are able to remember and reproduce simple shapes from memory, a discovery that could lead to better diagnosis and treatment of memory impairments in humans.
“Our observations of recall in Old World monkeys suggest it may have been adaptive in primates long before humans evolved, and that it does not depend on language or anything else that is uniquely human,” says Ben Basile, researcher at the Yerkes National Primate Research Center at Emory University.
Basile and Robert Hampton developed a computer touchscreen method to test the recall power of rhesus monkeys. The findings are published in the journal Current Biology.
“We believe we have found a new method for testing animals that opens a whole new window into the world of nonhuman memory research,” he says. “For the first time, monkeys can actually show us what they recollect, and their test results are directly comparable to human tests.”
Human tests may involve recall, retrieving information about something that isn’t present, like being able to draw the face of someone met the day before—or recognition, that demonstrates the ability to detect that something is familiar when it is seen again.
Previous research has established the ability of monkeys to recognize objects, but the lack of language has hindered efforts to test that ability.
The language barrier was broken by teaching the monkeys to draw.
The monkeys were shown simple two- and three-box shapes on a computer screen. Later, they were presented with a computer touchscreen that allowed them to recreate those shapes by touching the corresponding areas of a grid. The monkeys learned through trial and error that reproducing the shapes they had seen previously would bring a food reward. Once trained, the monkeys were able to transfer their memory skills to novel shapes.
The performance of the monkeys on the computer touchscreen paralleled that of humans using a standard human recall test, in which subjects draw a complicated shape from memory.
Different types of memory may have evolved to solve distinct problems. Recognizing something as familiar, for instance, is quick and might allow for rapid responses to sightings of food and predators. Recollecting absent information is slower, but supports a more detailed and flexible use of memory.
A rare case of amnesia causes humans to be able to recognize objects before them, but not be able to recall those same objects when they are out of sight.
The researchers speculate that recollection might help monkeys return to out-of-sight places where they previously found food, or to flexibly plan social interactions with other monkeys based on previous behavior.
“Humans certainly recall more complex and sophisticated things over longer time periods,” Basile says. “But we’ve shown that for simple shapes, monkeys have a pattern of performance for recognition and recall that mirrors that of humans. And their ability to immediately transfer their performance to new shapes suggests we’re tapping into some general cognitive capacity.
“With this type of information, we are moving closer to better diagnosing and developing treatments for memory impairments in humans.”
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