Biological origins of number perception
09.09.2025
A study from the Department of General Psychology at the University of Padua demonstrates that the association between numbers and space depends on brain lateralisation and light exposure. Many of us imagine numbers arranged along a mental line running from left to right, with smaller numbers on the left and larger ones on the right. This "mental number line" is commonly thought to be a product of cultural experience, particularly reading and writing. However, studies on children and animals suggest that this association may have biological origins, rooted in brain lateralisation, which is the specialisation of the brain's two hemispheres for different functions.
The research published in the journal «eLife», coordinated by the Department of General Psychology at the University of Padua, provides direct evidence supporting this hypothesis by observing newly hatched chicks. The results indicate that brain lateralisation, the specialisation of the right and left hemispheres for different functions, is crucial for developing a left-to-right oriented mental number line and is influenced by light exposure.
Rosa Rugani, the study's lead author and a lecturer at the Department, explains that light exposure during embryonic development induces brain lateralisation in domestic chicks, enhancing their spatial-numerical abilities and their tendency to "count" from left to right. Although various theoretical models had hypothesised that the mental number line originates from brain lateralisation, direct experimental evidence was lacking until now. Their study provides these evidences.
The research showed that only individuals with well-developed lateralisation tended to organise numbers from left to right. Rugani emphasises that for the first time, it is demonstrated that lateralisation is not just associated with the mental number line but is essential for its development. "For the first time, we demonstrate that lateralisation is not just associated with the mental number line but is essential for its development," Rugani points out. This suggests that our perception of numbers in space has deep biological roots, although it is later shaped by interaction with the environment.
This suggests that our perception of numbers in space has deep biological roots, although shaped by interaction with the environment.
Hence follows the hypothesis that this tendency might have evolutionary advantages. Understanding the biological foundations of numerical cognition can help us understand why and when certain abilities emerge and why they may be altered in the presence of atypical brain organisation. This research, therefore, opens new perspectives in studying the evolutionary origins of numerical thinking and the influence of early sensory experiences on cognitive development.
