A big brain may not be necessary to do maths. Honeybees have passed a test of arithmetic that may require them to add and subtract, although others have questioned if that is really the case.

In the test, bees were first shown a picture containing between one and five shapes. Then they were given a choice of two chambers, each with another picture by the entrance. One chamber contained a drop of sugar solution as a reward; the other contained bad-tasting quinine solution.

If the shapes in the first picture were blue, the bees had to add one to the number of shapes to choose the correct chamber. If the shapes were yellow, they had to subtract one.

Fourteen bees each went through the exercise 100 times during the training phase. In subsequent tests, bees chose the correct answer 67.5 per cent of the time – significantly better than chance.

The correct answers in the tests were numbers that were not rewarded during training, so the bees could not get it right by simply associating a number with a reward. Sometimes the incorrect answer was in the same numerical direction as the right answer, so the test was more complicated than understanding whether the answer is bigger or smaller than the first number.

This is a hard task for bees, says Adrian Dyer of RMIT University, Australia. It requires them to memorise the colour rule and apply it to the number of shapes in working memory.

## Another explanation

Clint Perry at Queen Mary University of London, UK, thinks the idea that bees are doing arithmetic doesn’t add up. If the bees simply choose the picture most similar to the picture they saw first, they could get 70 per cent correct.

“The ability to add and subtract is a higher level cognitive ability,” he says. “To claim that an insect can do this is extraordinary and therefore requires extraordinary evidence.”

Many animals seem to be able to count, but few have demonstrated a knack for arithmetic. Elephants seem to be capable of simple calculations, and so do newborn chicks.

Among invertebrates, evidence of numeracy is sparse, although one study found that spiders can count prey items they keep in a “larder” and notice when one is added or removed. Dyer’s team previously found that bees could recognise zero as a number smaller than one.

It’s unclear whether bees in nature use numerical processing in some way, or if the ability is the result of a general capacity to learn how to solve new problems. Since bees take some time to learn the problem, the latter seems more likely, says Dyer.