by FIONA MACRAE

Last updated at 00:37 18 December 2007

We like to think they have mischief rather than maths on their minds.

But monkeys, it seems, are a whizz at mental arithmetic.

Research shows that the creatures are almost as good as humans at doing sums in their heads, adding up numbers with amazing accuracy.

Faced with 40 addition problems, two rhesus macaque monkeys scored nearly as well as a group of college students.

Scroll down for more...

The researchers, from Duke University in North Carolina in the U.S., described the results as "striking".

They said: "We know that animals can recognise quantities but there is less evidence for their ability to carry out explicit mathematical tasks, such as addition. Our study shows that they can."

They started by training two female monkeys, named Feinstein and Boxer, to do simple sums.

The creatures were placed in front of a computer screen and watched while two sets of dots flashed up.

They were then presented with two more sets of dots enclosed in boxes, one of which represented the sum of the first two sets of dots and one representing a different number.

For example, they could have been shown two dots and four dots, followed by a choice of six dots - the right answer - or eight dots - the wrong answer.

Every time they made the right choice, they were rewarded with some fruit juice.

The monkeys quickly grasped the concept and were soon pitted against the college students.

Both monkeys and people were then given 40 simple addition sums to solve.

In the case of the monkeys, the problems were all ones they hadn't seen before.

The monkeys picked the right answer 76 per cent of the time.

The students managed a 94 per cent success rate, the journal PLoS Biology reports.

The study follows recent research showing chimps can beat humans in a memory test.