Bees sort 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 begin to arrange increasing amounts 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 that is read from right to left.
“The issue is still being debated between those who think the mental number line is innate and those who say it is cultural,” said Martin Giurfa, a professor at the Animal Cognition Research Center at Paul Sabatier University in Toulouse, France. .
There has been recent evidence that newborns and some vertebrates, 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), with the aim of finding out if the same happens with insects, using an experiment with bees.” It has already been shown that bees are able to count , at least up to five,” Giurfa told AFP.
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.
A numbers game
For the experiment, the researchers flew individual bees into the first of two compartments in a wooden box. Sugar water was then used to entice the bees to select a number placed in the middle of the back of the second compartment.
The number remained the same for each individual bee, but varied randomly in the cluster between one, three, or five, in the shapes of circles, squares, or triangles. Once the bees were trained to fly to their set number, the researchers removed it and put another number on either side of the second compartment, leaving the middle blank.
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Then they removed the sugar-water reward and watched where the bees went. For example, if the bee was trained to select the number three, and now faced with two numbers one on either side and nothing in between, which way did they fly?
About 80 percent of the time, the bees chose the option on the left, the “correct choice” if brains order numbers from left to right, Giurfa said. But if those same bees were given two number fives to choose from, they did well, again supporting the mental number line.
And the bees trained to go for the number one went right for the number three, while the bees trained to go for a five went left for their three. So if animals think in numbers from left to right, why isn’t this true for all humans?
Giurfa said it was more complicated than choosing directly between nature and nurture. Although 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.