Biology subjects

Rugani, R.

Publications and source records attributed to Rugani, R..

5 recordsLinked to original sources

bioRxiv2026

The Privileged Link Between Number and Space: Day-old Chicks (Gallus gallus) Show Spatial-Numerical but Not Spatial-Quantity Associations

Spatial-numerical association reflects an internal "mental number line" where numerosities are mapped from left to right in space. While evidence from 8- to 9-month-old human infants suggests a privileged link between number and space, these findings do not definitively establish whether discrete numerosity or continuous quantity is the primary driver of spatialization due to the relatively extensive postnatal experience. Using domestic chicks (Gallus gallus), a model testable with minimal postnatal experience, we investigated precocial predispositions to map both discrete numerosities and continuous quantity (physical size) onto space. In Experiment 1, we replicated spatial-numerical association: chicks associated relatively smaller numerosities with the left hemispace and larger ones with the right hemispace. In Experiment 2, however, spatial-quantity association for physical size was asymmetric: chicks showed a rightward preference for smaller sizes and no congruent small-left/large-right mapping. Together with infant data, these findings indicate that a generalized and congruent spatial-magnitude association does not emerge at the earliest stages of development, and challenge accounts positing that spatial mappings for continuous magnitudes precede and underpin the spatial organization of number.

animal behavior and cognition↗

bioRxiv2026

Space-number association in zebrafish

Spatial-numerical associations reflect the tendency to map small numerosities to the left and larger numerosities to the right. Although widely documented in humans and some non-human species, its presence in teleost fish has remained unclear. Here, we investigated whether zebrafish exhibit a spatial-numerical association by presenting fish with a left-right numerical discrimination task in a controlled behavioral assay. Zebrafish showed a reliable leftward preference when selecting smaller numerosities and a rightward preference when selecting larger ones, indicating a systematic coupling between numerical magnitude and spatial direction. These results provide the first evidence of a number-space association in zebrafish and demonstrate that number-space mapping extends to a basal vertebrate lineage. This establishes zebrafish as a tractable model for probing the neurobiological foundations of number-space associations. HighlightsO_LIZebrafish map numerical magnitudes onto left-right spatial positions. C_LIO_LISpatial biases are more robust for small numerosities but still present for larger ones. C_LIO_LIContinuous physical controls disproportionately affect the strength of spatial mapping for large sets. C_LI

animal behavior and cognition↗

bioRxiv2025

Hatching with Numbers: Pre-natal Light Exposure Affects Number Sense and the Mental Number Line in young domestic chicks

Humans order numerosity along a left-to-right Mental Number Line (MNL), traditionally considered culturally rooted. Yet, some species at birth show Spatial-Numerical Associations, SNA, suggesting neural origins. Various accounts link SNA to brain lateralization, but lack evidence. We investigated brain lateralization effects on numerical spatialization in 100 newborn domestic chicks. In-ovo light exposure yielded strongly-lateralized brains in half the chicks and weakly-lateralized in the other half. Chicks learned to select the 4th item in a sagittal array. At test, the array was rotated 90{degrees}, with left and right 4th items correct. Strongly-lateralized chicks outperformed weakly-lateralized ones when ordinal and spatial cues were reliable (experiment 1), but not with unreliable spatial cues (experiment 2). Moreover, only strongly-lateralized chicks showed left-to-right directionality, suggesting the right hemispheres key role in integrating spatial and numerical cues. We demonstrate that brain lateralization is fundamental for developing a left-to-right oriented SNA.

animal behavior and cognition↗

bioRxiv2024

Symbolic and Non-Symbolic numbers differently affect centre identification in a number-line bisection task

Numerical and spatial representations are intertwined as in the Mental Number Line, where smaller numbers are on the left and larger numbers on the right. This relationship has been repeatedly demonstrated with various experimental approaches, such as the line bisection task. Spatial accuracy appears to be systematically distorted leftward for smaller digits by elaboration of spatial codes during number processing. Other studies have investigated perceptual and visuo-spatial attention bias using the digit line bisection task, suggesting that these effects may be related to a cognitive illusion in which the reference numbers project their values onto the straight line, creating an illusory lateral disparity. On the other hand, both dot arrays (non-symbolic stimuli) and arabic numbers (symbolic stimuli) demonstrate a privileged relation between spatial and numerical elaboration. The bias toward the larger numerosity flanker was attributed to a length illusion. There is, however, no consensus regarding whether physical features and symbolic and non-symbolic numerical representations exert the same influence over spatial ones. In the present study, we carried out a series of 4 Experiments to provide further evidence for a better understanding of the nature of this differential influence. All experiments presented the numbers in both symbolic and non-symbolic formats. In Experiment 1, the numbers "2-8" were presented in a variety of left-right orientations. In Experiment 2, the flankers were identical, "2-2" or "8-8", and symmetrically displaced with respect to the line. In Experiment 3, we employed asymmetrically distributed eight dots, or font sizes in "8-8" numerals, to create a perceptual imbalance. In Experiment 4, we replicated the manipulation used in Experiment 3, but with two dots and "2-2" numerals. The Non-Symbolic format induced stronger leftward biases, particularly when the larger numerosity (Experiment 1) or the denser stimuli near the line (Experiments 3 and 4) were on the left, while no bias emerged when flankers were numerically equivalent and symmetrical (Experiment 2). The left bias may result from a tendency to estimate the influence of stimulus perception associated with participant scanning direction, similar to the direction of pseudoneglect. Conversely, the Symbolic format induced mostly right bias, possibly due to left-lateralized processing and a tendency to use a common strategy involving scanning from left to right. Altogether our data support the view that abstract numbers and non-symbolic magnitude affect perceptual and attentional biases, yet in distinctive ways.

neuroscience↗

bioRxiv2017

A mental number line in human newborns

In the 19th century Francis Galton first reported that humans represent numbers on a mental number line with smaller numbers on the left and larger numbers on the right. It has been suggested that this orientation emerges as a result of reading/writing habits for both words or numbers. Recent evidence in animals and infants in the first months of life has challenged the primary role of language in determining the left-to-right direction of spatial-numerical association, SNA. However, the possibility that SNA is learnt by early exposure to caregivers directional biases is still open. Here we show that 55-hour-old newborns, once habituated to a number (i.e., 12), spontaneously associated a smaller number (i.e., 4) with the left side and a larger number (i.e., 36) with the right side of space. Moreover, SNA in neonates was not absolute but relative. The same number (i.e., 12) was associated with the left side whenever the previously experienced number was larger (i.e., 36), but with the right side whenever the number was smaller (i.e., 4). Control on continuous physical variables showed that the effect was specific of discrete magnitudes. Hence, soon after birth humans associate smaller numbers with the left space and larger numbers with the right space. These results constitute strong evidence that in our species SNA originates from pre-linguistic and biologically precursors in the brain.\n\nSIGNIFICANCE STATEMENTFor human adults, the representation of number and space is profoundly intertwined. Humans represent numbers on a left to right oriented Mental Number Line (MNL), with small numbers located on the left and larger ones on the right. How do these connections arise? Do we learn to associate numbers with space throughout cultural learning and social interactions or is this association rooted in the biology of the human brain? We showed that neonates spontaneously associate numbers with space. After being habituated to a certain number, neonates associated a smaller number with the left and a larger number with the right side. This evidence demonstrates that a predisposition to map numbers onto space is rooted in human neural systems.

neuroscience↗