Picture a number line running from the smallest to the largest values. New research reveals that the human brain employs a comparable system when comparing numbers. Scientists have identified a “mental map” where numbers possess unique coordinates, potentially aiding in ordering them by magnitude.
“Numbers are abstract concepts, but our brains have ways of organizing them that allow us to compare and reason about their values,” explained study co-authors Daniela Valério, a postdoctoral researcher at the INSERM-CEA Cognitive Neuroimaging Unit (UNICOG) in France, and Stanislas Dehaene, director of UNICOG.
“What is fascinating is that the brain can bring together numbers that look very different, such as integers [whole numbers] and fractions, within a common system,” they stated in an interview with Live Science.
This shared mapping system was detailed Thursday (Oct. 22) in the journal PLOS Biology.
To explore how the brain represents different types of numbers, Valério, Dehaene, and their team used high-resolution functional magnetic resonance imaging (fMRI) to track blood flow as an indicator of neural activity. They monitored brain responses in 20 adults as participants compared various numerical values—both fractions and whole numbers—and determined whether each was greater or smaller than the preceding one.
The scans revealed distinct activity patterns in the anterior inferior parietal cortex, a brain region known for its role in numerical processing. As participants evaluated numerical values, this area activated in an organized pattern resembling a number line. Both whole numbers and fractions were positioned along this shared continuum according to their magnitude, rather than being processed through separate neural pathways.
The brain’s shared map integrates different number formats into a unified system based on their quantitative values, the researchers concluded.
“For me, it is how the brain gets from a symbol to its meaning,” noted Abiot Derbie, a cognitive neuroscientist and founder of LifeByLogic, who was not involved in the research.
The fraction “¼” contains the digit “4,” but its actual value is much closer to zero, Derbie pointed out. “The activity patterns reflected that numerical relationship, going beyond the digits themselves,” he told Live Science via email.
While the brain’s representation of numerical magnitude in the parietal lobe is well-established, previous understanding focused primarily on whole numbers. The neural strategy for processing fractions remained unclear until this study, which advances prior research by examining how both number magnitude and format are processed simultaneously.
“To the best of our knowledge, this is the first study to investigate the geometry of neural representations in a task involving both integers and fractions,” the researchers wrote.
“In the future, it might be interesting to expand the present work to decimal numbers.”
Previous studies showed that fractions and whole numbers activate overlapping regions of the brain’s number-processing network, according to Derbie. “This study gives us a clearer picture of how their values are organized.”
Future research could investigate how this neural representation varies across individuals of different ages, educational backgrounds, and mathematical proficiency levels. The current study included only native French speakers, limiting generalizability across languages and cultures.
“I would want to see how this organization develops as people learn,” Derbie suggested. Tracking children before and after learning about fractions could reveal whether changes in brain activity correspond with improved comprehension.
In the present study, participants found comparing fractions more challenging than whole numbers, exhibiting slower responses and more errors—findings consistent with educational research. However, the results do not address why fractions prove harder to process.
“Our study was not designed to explain why fractions are harder to learn or understand,” Valério and Dehaene clarified. “What is new in our study is that we show that these different types of numbers are organized within a shared map in the brain.”
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Valério, D., Debray, S., Karami, A., Cauté, M., Gravel, N., & Dehaene, S. (2026). A cortical semantic map integrates fractions and integers in the human brain. PLOS Biology, 24(10), e3003820.