Imagine a number line stretching from the smallest value to the largest. New research suggests the human brain uses a similar system when comparing numbers.

Scientists have identified a “mental map” in which numbers are assigned unique coordinates in the brain according to their magnitude. The finding may help explain how people arrange numbers in order and reason about their values.

“While numbers are abstract concepts, our brains have ways of organizing them, allowing us to compare and reason about their values,” study co-authors Daniela Valério, a postdoctoral researcher at the INSERM-CEA Cognitive Neuroimaging Unit in France, and Stanislas Dehaene, director of the unit, told Live Science in a joint statement.

Whole numbers and fractions share a brain map

“What’s interesting is that the brain can put together numbers that look very different, such as integers [whole numbers] and fractions, within a common system,” the researchers said.

To investigate how the brain represents different types of numbers, Valério, Dehaene and their colleagues used a high-resolution functional magnetic resonance imaging (fMRI) scanner. The technology tracks blood flow in the brain as an indirect measure of neural activity.

The researchers scanned the brains of 20 adults while they compared pairs of whole numbers and fractions. Participants had to decide whether each number was greater than or less than the number that came before it.

The study was published Thursday, October 22, in the journal PLOS Biology.

Brain activity resembled a number line

Brain scans revealed distinct patterns of activity in the anterior inferior parietal cortex, a region known to play an important role in number processing.

As participants compared numbers, activity in this region formed an organized pattern resembling a number line. Whole numbers and fractions appeared along the same neural map according to their size, rather than being represented by entirely separate systems.

The researchers concluded that this shared brain map places different numerical formats into a common system based on the quantities they represent.

Why the symbols themselves are not enough

The results suggest that the brain responds to the relationship between numbers, not simply to the symbols used to write them.

For example, the fraction “1/4” contains the digit “4,” but its value is much closer to zero. Activity patterns appear to reflect the numbers’ actual relationships and magnitudes rather than the individual digits within them.

Previous research has shown that the parietal lobe is involved in representing numerical magnitude. Scientists also knew that fractions and whole numbers engage overlapping parts of the brain’s number-processing network. However, the way the brain represents fractions—and how it combines them with whole numbers—was less clear.

Fractions were harder for participants to compare

Participants were slower and made more errors when comparing fractions than when comparing whole numbers. That result was expected, but the study was not designed to explain why fractions are more difficult to learn or understand.

“What’s new in our study is that we show that these different types of numbers are organized within a shared map in the brain,” Valério and Dehaene told Live Science.

What researchers want to study next

“To our knowledge, this is the first study to investigate the geometry of neural representations in a task involving both whole numbers and fractions,” the researchers wrote in their report.

They suggested that future research could examine how the brain represents decimal numbers. Researchers could also investigate whether this neural organization differs according to age, educational background or mathematical experience.

The study included only native French speakers, so the results may not capture differences between languages and cultures.

Another potential avenue would be to track children before and after they learn about fractions. That could reveal whether changes in brain activity accompany improvements in understanding.

“I’m looking forward to seeing how this organization develops as people learn,” cognitive neuroscientist and LifeByLogic founder Abiot Darby said.

Study details

Valério, D., Debray, S., Karami, A., Cauté, M., Gravel, N., and Dehaene, S. (2026). “Cortical semantic maps integrate fractions and whole numbers in the human brain.” PLOS Biology, 24(10), e3003820.

Find out how much you know about the human body’s most complex organ with this tool: Brain quiz.