Monkey maths: greater than or less than yours?

By Joseph Milton

We knew that monkeys are adept at counting, adding-up and multiplication. They can even grasp abstract mathematical concepts, suggesting they’re a match for college students when it comes to maths.

Now, for the first time, researchers have demonstrated the neurological basis of monkeys’ understanding of abstract maths principles.

The team at the University of Tübingen, led by Andreas Nieder, used special probes to measure the electrical activity of individual neurons – brain cells – in the prefrontal cortex (PFC) of rhesus monkeys as they performed tasks responding to stimuli which they had been trained to recognise as representing “greater than” or “less than” rules.

Their previous work on rhesus monkeys showed that neurons become dedicated to specific numbers, and this new research goes a step further, indicating that individual PFC neurons have the capacity to represent flexible mathematical rules.

Spikes in electrical activity were seen as the rules were being followed in about twenty per cent of the neurons studied, indicating that they encode the rules. About half were dedicated to the ‘greater than’ rule, and the other half, to the ‘less than’ rule.

“It seems the brain operates with specific ‘rule-coding’ units that control the flow of information between sensory, memory and motor stages,” said Professor Nieder.

Elizabeth Brannon of Duke University, who first showed that monkeys could learn abstract principles of mathematics said: “This study shows that neurons in the PFC are encoding the meaning of the rule…responding selectively to either the greater than or less than relationship.”

In humans, PFC lesions lead to problems in following strategies and pursuing long-term goals, while sensation and memory remain unaffected. This research could help understand what goes wrong when this part of the brain is damaged.

It is also further evidence of the existence of an evolutionarily primitive system in primate brains for understanding maths. The ancestors of humans and rhesus monkeys diverged about 20 million years ago, so numerical skills must have evolved before then.

Journal reference: PNAS (DOI:10.1073/pnas.0909180107)

This entry was posted on 4 February, 2010 at 16:33 and is filed under News & discovery. You can follow any responses to this entry through the RSS 2.0 feed.