Bees "count" from left to right, like humans

Even before learning to count, Man has the ability to mentally order increasing quantities by going normally from left to right.

But in cultures using right-to-left writing, such as Arabic script, this order is reversed.

Consequently, "the subject remains debated with those who think that the mental digital line has an innate character and those who say that it is cultural", remarks to AFP Martin Giurfa, professor at the Center for Research on Animal Cognition. at the University of Toulouse III – Paul Sabatier.

However, as the study published in October in the Proceedings of the American Academy of Sciences (PNAS) reminds us, recent work on newborns and other vertebrates, in particular primates, has shown an innate meaning to this mechanism, from left to right.

The experiment carried out by Pr. Giurfa's team confirms these discoveries with the demonstration of an identical mechanism in an emblematic species of invertebrate: the bee.

“We have already shown that bees are able to count, at least up to five” and that they process information differently between their two cerebral hemispheres, recalls Prof. Giurfa.

This difference in treatment is also present in humans, where it is "one of the reasons invoked for the existence of the digital mental line".

A bee, a crate

In short, the researcher wondered, could it be that the bee brain "aligns the numbers like we do ourselves?"

In other words, "if I am using +one+ as a reference, +three+ is on my right, but if I am using +five+ as a reference, +three+ is on my left".

His experience, imagined with Catherine Thevenot, from the University of Lausanne, and Rosa Rugani, from that of Padua, is based on the following device: a box whose interior is separated by a partition.

The bee is accustomed, after having crossed this partition, to find in the compartment a single label always bearing the same number of figures, but of aspect varying at random.

Namely, one or three or five circles, squares or triangles.

With the reward, as soon as they hit the target, a sweet solution dispensed by a small pipette placed in the center of the label.

Once used to it, the bee is this time faced with two identical labels but bearing a number of figures different from that of the training, and located at the bottom of the compartment, on the left and on the right.

Right and left

For example, bees trained to receive a reward with a label comprising three figures are confronted with two identical labels bearing a single figure.

Result, "overall they make the right choice at 80%", moving towards the figure on the left, explains Pr. Giurfa, since one is less than three.

And if they are presented with two labels each bearing five figures, they move to the right, since five is greater than three.

The result is identical for bees accustomed to a reward with a label bearing a single figure, which go towards the label on the right when it has three figures, and for bees accustomed to a label bearing five figures, which tend to go towards the left when presented with only three.

Bees order numbers well on a mental number line, from left to right.

But why would some humans be spared this mechanism?

Rather than a binary choice between innate and acquired, Pr. Giurfa prefers to defend the idea that "this representation of numbers being innate, culture can qualify it, even reverse it, or on the contrary accentuate it".

The bee, on the other hand, obviously sticks to what nature tells it to do.

© 2022 AFP