Paris (AFP)

The human being would be endowed with an innate capacity to distinguish geometric shapes, signing his singularity vis-a-vis other primates, unable to learn this "language", according to an empirical study of researchers in neuroscience.

From the earliest engraving attributed to Homo sapiens - parallel lines dating back 73,000 years - to houses drawn by modern children from an early age, the taste for regular geometric shapes is universal among humans.

He indicates that humans have a symbolic "language of thought" undoubtedly specific to their species, according to the study signed by doctoral student Mathias Sablé-Meyer, of the University of Paris-Saclay (PSL) / Collège de France.

A team of researchers from NeuroSpin (the CEA's brain imaging research center led by neuroscientist Stanislas Dehaene) conducted an experiment showing "that geometry intuitions are present in humans, but absent in baboons," says the study published in late April in the Proceedings of the American Academy of Sciences.

The experiment consists of "finding the odd one out" among six simple geometric shapes - quadrilaterals - only one of which has an irregularity, such as a slightly longer side, a parallelism error or a different angle.

Then to repeat the operation, still with a quadrilateral, but more and more complex.

- Kindergarten children -

It exploits the effect of geometric regularity, which postulates that one locates the intruder all the more simply and quickly that the examined form is a regular figure, like a square.

And that conversely, it is more difficult to locate it when the figure is more complicated, going from the rhombus to the trapezoid, to an irregular quadrilateral, that is to say without right angles or identical or parallel sides.

Typically the tested human almost always finds the intruder among the squares.

Its error rate rises to 40% with an irregular quadrilateral.

With the collaboration of Joël Fagot, of the cognitive psychology laboratory of the CNRS (Aix-Marseille University), baboons were trained in this game. With excellent results with non-geometric images, like a red cherry to be distinguished in the middle of watermelon slices.

But as soon as they switched to geometric shapes, "their performance fell apart," according to the study.

"Baboons are wrong everywhere", whatever the form, explained to AFP Mathias Sablé-Meyer.

Easy, the skeptics will say.

Adults do better than baboons because they have learned their geometry lessons.

And no!

Because even if they are less efficient at the task, we observe the same effect of geometric regularity in kindergarten children, barely out of the age of playing cube, and in those in the first year of school. primary.

- Nomads of Namibia -

Still easy, the most skeptical would say, the children tested having rudiments of geometry, and living in a universe made of lines and angles.

And still missed.

The researchers, with the help of Serge Caparos, of the psychology department of Paris-8 Nanterre, took the test to adult Himbas, a pastoral people in northern Namibia.

With results comparable to those of young French children.

Yet "we know that they have no names for geometric shapes, nor formal education on their properties," recalls Mr. Sablé-Meyer.

Nomads, they also live in a "non-structured" environment, free from geometric shapes, underlines the study, which compares that of the baboons tested, who "grew up in a very constructed laboratory environment".

The researchers conclude that humans have a capacity for symbolic abstraction, a "language" using notions such as right angles or parallelism, which are specific to them.

They confirmed their proposal using two artificial intelligence models.

The first, which "superficially copies the structure of the visual cortex" - linked to perception spots - predicts the behavior of baboons rather well.

But to account for that of humans, it is necessary to go through a second, by feeding it "symbolic information, the principles of Euclidean geometry".

The study carries a quote from Galileo, for whom the Universe "is written in mathematical language, and its characters are triangles, circles and other geometric shapes, ...".

© 2021 AFP