Rhesus macaques have neurons dedicated to 'less than,' 'greater than' problems, study suggests
TUESDAY, Jan. 19 (HealthDay News) -- Monkey see, monkey do simple math?
A German team of neurobiologists has found that rhesus macaques can engage in abstract mathematical reasoning using specific brain cells dedicated to the comprehension of math rules and relationships.
The finding could provide insight into the neurology behind human ability to comprehend much more complex mathematics, German scientists said.
"Even simple mathematical operations are highly abstract mental operations on quantities that are governed by overarching concepts and principles," explained study co-author Andreas Nieder, a professor in the department of animal physiology at the University of Tubingen's Institute of Neurobiology. "Monkeys can adopt abstract mathematical rules, and they can switch between them."
"That means they understand very fundamental, non-symbolic mathematical principles, such as 'greater than' and 'less than'," Neider added. His team traced this ability to neurons in the prefrontal cortex region of the primate brain -- an area that appears to be devoted to encoding the basic rules of math.
Neider and co-author Sylvia Bongard reported their findings online Jan. 18 in the Proceedings of the National Academy of Sciences.
To assess primate math skills and isolate the neurology behind them, the team trained two rhesus monkeys to assess when groups of various objects, such as dots, were either "greater than" or "less than" another grouping of the same object.
Having learned these two basic mathematical rules, the monkeys were then tracked as they worked levers to indicate which grouping was the larger or smaller of the two displayed.
During the course of 160 different trials, the authors also recorded neural activity among 484 randomly selected cells located in the monkey's cognition center in the brain, the prefrontal cortex.
Neider and his team found that the monkeys were able to successfully execute the "greater than" and "less than" rules -- and switch back and forth between the two -- between 83 and 92 percent of the time.
What's more, 20 percent of the monitored neurons appeared to be specifically tasked with facilitating this type of abstract math-rule comprehension. The cells did so independently, while other cells focused on the processing of sensory information, such as visual and/or or memory cues.
This isn't the first indication that primates possess some degree of mathematical talent. Last year, Duke University researchers working with macaque monkeys found that the primates are capable of basic math despite their lack of language skills. And in 2007, researchers from Japan's Kyoto University found that young chimpanzees actually out-performed human adults in tracking numbers and remembering sequencing.
And math proficiency may not be unique to primates.
"Number crunching is a widespread skill among animals," Neider said. "So far, several mammalian and bird species have been shown to possess it, as well as salamanders, fish, and even bees. This ability has obvious survival advantages. In foraging, for instance, it is an advantage to choose the food source with more items compared to few. Also in social interactions, it pays to know the number of individuals in one's own group as compared to an opponent party before deciding whether to flee or attack."
Nevertheless, Neider noted that human mathematical cognition remains leaps and bounds ahead of that of other animals.
"In all animals," he said, "set size is never represented in a precise way -- exactly five objects -- but always approximately, 'about' five items. Amongst other things, this sets us apart from all other animals. Guided by the development of language, we acquire a very precise understanding of numbers. We denote numbers symbolically, a skill beyond the scope of any animal."
"With such mental tools at hand and sophisticated logical abilities, we structure and process numerical information in the most sophisticated ways," Neider observed, "and with the most impressive results."
"It's simply a question of the much greater extent to which we, as humans, use abstract reasoning to maneuver in our environment, relative to other animals," added Joe Verghese, associate professor of neurology at the Albert Einstein College of Medicine in New York City.
"So while the idea that monkeys can perhaps specifically engage in abstract mathematical reasoning is, I believe, something new, there have been many previous experiments that have shown that primates do engage in abstractions," he added. "Which means that we are -- humans and animals -- probably all hardwired to do some kind of abstract reasoning. But it's a question of the pecking order, of sophistication. The question then is, do primates consider what is life? What comes after death? Unfortunately, I don't think there are experiments on that level yet."
For more on the brain, head to the U.S. National Institute of Neurological Disorders and Stroke.
SOURCES: Andreas Nieder, Ph.D., professor, department of animal physiology, Institute of Neurobiology, University of Tubingen, Tubingen, Germany; Joe Verghese, M.B., B.S., associate professor of neurology, Albert Einstein College of Medicine, New York City; January 18-24, 2010 (online), Proceedings of the National Academy of Sciences.
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