How Brain Asymmetry Influences the Development of the Mental Number Line in Early Life

Recent research published in eLife reveals that brain lateralization—the specialization of the brain's hemispheres—plays a fundamental role in shaping how young animals and humans develop a mental representation of numbers. The study, conducted by Rosa Rugani and colleagues, highlights that the tendency for the left and right sides of the brain to assume distinct functions influences the perception of numerical order, specifically the familiar left-to-right mental number line. This spatial-numerical association appears to be rooted in biological processes rather than solely cultural factors.

The researchers investigated this phenomenon using domestic chicks, providing insights into the developmental origins of numerical cognition. By exposing chick embryos to light during critical periods of development, they successfully induced brain lateralization. After hatching, the chicks were trained to locate food among a series of identical objects arranged vertically. When the arrangement was rotated horizontally, dominant lateralized chicks showed a preference for choosing the item corresponding to the number four from the left, indicative of a natural left-to-right numerical mapping. Conversely, chicks with less lateralization displayed no consistent directional bias.

Further experiments demonstrated that the chicks’ ability to perform this spatial-numerical task depended on which eye they used, as each eye primarily connects to the opposite brain hemisphere. Chicks using only their left eye (right hemisphere engaged) consistently preferred the left-side number, reinforcing the significance of hemispheric specialization in numerical cognition. When the spatial arrangement became unreliable, the chicks' preference disappeared, emphasizing that brain lateralization is crucial for linking space and number.

The findings suggest that the brain's asymmetrical structure predisposes animals, including humans, to develop spatial-numerical associations early in life. These biological foundations could offer advantages in natural settings, such as efficient foraging or quantifying resources. Importantly, this research supports the idea that our sense of number and space is inherently grounded in brain organization, with environmental influences shaping its development.

This study advances our understanding of how early sensory experiences and brain asymmetry contribute to cognitive skills like numerical understanding. It opens avenues for exploring developmental anomalies and the evolutionary significance of lateralization in cognitive functions.

Source: Medical Xpress