Sep 9, 2025 08:29 PM
(This post was last modified: Sep 9, 2025 08:33 PM by C C.)
https://www.eurekalert.org/news-releases/1097668
EXCERPT: Lateralisation of the brain – the tendency for the left and right hemispheres to specialise in different functions – underlies the development of a left-to-right mental number line, according to a study in newborn chicks.
The study, published as a Reviewed Preprint in eLife and appearing today as the final version, is described by the editors as fundamental. They say the evidence presented is compelling and the results will be of interest to researchers studying numerical cognition, brain lateralisation, and cognitive brain development more broadly.
Many people intuitively think of numbers as arranged along a mental line, either running from left to right, with smaller numbers on the left and larger on the right, or vice versa. This representation – often called the mental number line – is traditionally thought to develop through cultural experience, especially through reading and writing direction. However, research has shown evidence of a left-to-right mental number line in young infants and animals, challenging this assumption and suggesting that this spatial-numerical association may have biological roots.
Brain lateralisation, also known as hemispheric specialisation, refers to the idea that the two hemispheres of the brain are functionally different and have specialised roles in various cognitive processes.
“Embryonic light exposure induces brain lateralisation in domestic chicks, and enhances their spatial-numerical abilities and their tendency to ‘count’ from left to right,” explains lead author Rosa Rugani, a Professor in the Department of General Psychology, University of Padua, Italy. “Although several models have proposed that the mental number line originates from brain lateralisation, direct evidence has been lacking. Our study provides this evidence, showing that lateralisation is essential for the emergence of left-to-right spatial-numerical associations.”
In domestic chicks, light exposure during embryonic development is known to promote brain lateralisation. Therefore, Rugani and colleagues incubated 100 chick eggs, half exposed to light and half kept in the dark. This produced a group of strongly lateralised chicks, and a group of weakly lateralised chicks.
[...] The authors suggest that a natural left-to-right scanning pattern may have evolutionary advantages for chicks. For example, when foraging it may allow them to efficiently locate and quantify food sources without overlooking areas.
“Our work demonstrates that lateralised brain function plays a key role in shaping how animals, possibly including humans, think about numbers,” says senior author Lucia Regolin, a Professor in the Department of General Psychology, University of Padua. “Understanding the biological basis of numerical thinking may help us identify why certain cognitive abilities emerge when they do in development, and why they might be altered in individuals with atypical brain organisation. This research opens the door to further studies on the developmental origins of numerical reasoning, and how early sensory experiences can influence later cognitive outcomes.” (MORE - missing details, no ads)
EXCERPT: Lateralisation of the brain – the tendency for the left and right hemispheres to specialise in different functions – underlies the development of a left-to-right mental number line, according to a study in newborn chicks.
The study, published as a Reviewed Preprint in eLife and appearing today as the final version, is described by the editors as fundamental. They say the evidence presented is compelling and the results will be of interest to researchers studying numerical cognition, brain lateralisation, and cognitive brain development more broadly.
Many people intuitively think of numbers as arranged along a mental line, either running from left to right, with smaller numbers on the left and larger on the right, or vice versa. This representation – often called the mental number line – is traditionally thought to develop through cultural experience, especially through reading and writing direction. However, research has shown evidence of a left-to-right mental number line in young infants and animals, challenging this assumption and suggesting that this spatial-numerical association may have biological roots.
Brain lateralisation, also known as hemispheric specialisation, refers to the idea that the two hemispheres of the brain are functionally different and have specialised roles in various cognitive processes.
“Embryonic light exposure induces brain lateralisation in domestic chicks, and enhances their spatial-numerical abilities and their tendency to ‘count’ from left to right,” explains lead author Rosa Rugani, a Professor in the Department of General Psychology, University of Padua, Italy. “Although several models have proposed that the mental number line originates from brain lateralisation, direct evidence has been lacking. Our study provides this evidence, showing that lateralisation is essential for the emergence of left-to-right spatial-numerical associations.”
In domestic chicks, light exposure during embryonic development is known to promote brain lateralisation. Therefore, Rugani and colleagues incubated 100 chick eggs, half exposed to light and half kept in the dark. This produced a group of strongly lateralised chicks, and a group of weakly lateralised chicks.
[...] The authors suggest that a natural left-to-right scanning pattern may have evolutionary advantages for chicks. For example, when foraging it may allow them to efficiently locate and quantify food sources without overlooking areas.
“Our work demonstrates that lateralised brain function plays a key role in shaping how animals, possibly including humans, think about numbers,” says senior author Lucia Regolin, a Professor in the Department of General Psychology, University of Padua. “Understanding the biological basis of numerical thinking may help us identify why certain cognitive abilities emerge when they do in development, and why they might be altered in individuals with atypical brain organisation. This research opens the door to further studies on the developmental origins of numerical reasoning, and how early sensory experiences can influence later cognitive outcomes.” (MORE - missing details, no ads)