Latest finding adds to theory that animals, including humans, naturally arrange things in a certain order, even without being able to count.
The study found that bees headed to the left to get a smaller number of items, and to the right to get a larger number of items. Photograph: Geoffrey Swaine/REX/Shutterstock
Bees order numbers in increasing size from left to right, a study has shown for the first time, supporting the much-debated theory that this direction is inherent in all animals including humans.
Western research has found that even before children learn to count, they start organizing growing quantities from left to right in what has been called the “mental number line”.
However the opposite direction has been found in people from cultures that use an Arabic script which reads from right to left.
“The subject is still being debated between those who think the mental number line has an innate character and those who say it is cultural,” said Martin Giurfa, a professor at the Research Center on Animal Cognition at Paul Sabatier University in Toulouse, France.
There has been recent evidence that newborn babies and some vertebrate animals, including primates, organize numbers from left to right.
Giurfa led a study, published last week in the journal Proceedings of the National Academy of Sciences (PNAS), aiming to find out if the same holds true for insects, via an experiment with bees.
“It has already been shown that bees are able to count – at least up to five,” Giurfa told Agence France-Presse.
They also process information differently in the two hemispheres of their brains, he added. This trait they seem to share with humans, and is thought to be a potential reason for the existence of the “mental number line”, Giurfa said.
For the experiment, the researchers had individual honeybees fly into a wooden box.
Sugar-water was then used to entice the bees to select an image displaying a number of items affixed to the walls of the box.
The number of items stayed the same for each individual bee, but varied randomly across the group – between one, three or five – and in terms of shapes: circles, squares or triangles.
Once the bees were trained to fly towards their set number of items, the researchers removed them and put out another number of items on the other sides of the boxes wall, leaving the middle blank.
They then removed the sugar-water reward and observed which way the bees went.
As an example, 80% of the bees who were trained to select the three items would head to the left when offered just one item on either side, and went to the right when offered five items on either side.
And bees trained to go for number one went to the right for a number three, while bees targeting a five went left for their three.
So if animals do in fact think of numbers from left to right, why is this not true for all humans? Giurfa said it was more complicated than directly choosing between nature and nurture.
Even if the mental number line “is innate, culture can still modify it, even reverse it – or on the contrary accentuate it,” he said.
Bees, on the other hand, have to stick to what nature dictates.