Innate Predispositions in Numerosity Cognition: A Cross-Cultural, Developmental, and Comparative Perspective

Numerical cognition and its underlying mechanisms have been extensively investigated because of their crucial role in the survival and reproduction of biological organisms. Evidence shows that animals possess a “number sense” to estimate quantities without counting, which assists behaviors such as foraging and social interaction. Thus, contrary to traditional beliefs that link numerical concepts only to language and culture, a growing body of research demonstrates that non-symbolic numerical cognition is shared across species, ages, and cultures. This number sense relies on the Approximate Number System (ANS), which is a fundamental cognitive mechanism that enables the estimation and comparison of quantities without the need for language or formal numerical symbols, such as digits or counting. The ANS supports the ability to make approximate judgments about the number of objects or events in a set and to perform basic arithmetic operations, such as addition and subtraction, although with inherent imprecision. Research has shown that many species, from primates to invertebrates, possess these abilities. For example, primates can perform numerical tasks and display ratio-dependent accuracy similar to humans, while domestic chicks show proto-arithmetic abilities comparable to those of human infants’. These findings suggest that the ANS might represent an evolutionarily ancient capability for processing numerical information, supporting the ability to navigate numerical tasks in natural environments. However, ongoing debates continue about the balance between innate predispositions and cultural influences on the ANS. In this thesis, we aimed to investigate key features of the ANS across different populations and species to deepen our understanding of the possible innate components of this system. In the first study, we investigated the Spatial-Numerical Association (SNA) phenomenon. Since its discovery, SNA has been largely attributed to cultural factors, such as reading and writing habits, while more recent research indicates that SNA is also manifested in individuals lacking cultural exposure, including non-human animals and pre-verbal children, suggesting that SNA may be influenced by both evolutionary and cultural factors. Thus we explored whether different SNA behaviors could emerge as a function of culture, age, and stimuli presentation. Results from Himba adults, Italian preschoolers, and Western adults revealed different SNA patterns in explicit and implicit tasks. Specifically, non-symbolic numerosities elicited a left-to-right SNA across all the populations in an implicit task, suggesting that SNAs are not solely the product of cultural influence. Additionally, we further investigated how symbolic and non-symbolic numerosities elicit asymmetrical SNA effects in literate adults. Our findings suggest that symbolic and non-symbolic numerosities might trigger distinct hemispheric activations thus affecting the directionality of SNAs. In the second study, we aimed to expand our understanding of numerical cognition in non-human animals (i.e., domestic chicks, Gallus gallus) by extending research from the visual domain to the auditory domain. Our findings demonstrated that the predispositions observed with visual stimuli are also present with acoustic stimuli, highlighting the consistency of the ANS across different sensory modalities. The role of potential confounding variables and the need for further research are discussed. In the third study, we examined another key aspect of the ANS, namely cross-modal numerical transfer. For both humans and non-human animals, the ability to assess and compare numerical quantities across different sensory modalities has been reported. Moreover, it has been demonstrated that multisensory information can improve numerical accuracy in children. Therefore, cross-modal numerical ability may offer evolutionary advantages, providing additional support for the idea that the ANS is shared and maintained across different species. We investigated this ability specifically in domestic chicks by presenting them with auditory and visual stimuli, both in spontaneous choice and imprinting paradigms. While our preliminary results may be not yet conclusive, they suggest the potential for cross-modal numerical abilities in chicks. Limitations of the current studies and proposals for further research are discussed. In summary, this thesis advances our understanding of numerical cognition by exploring SNA and numerosity perception across populations not subjected to cultural inputs. The findings point to a complex interaction between innate mechanisms and cultural influences, with implications for both human and animal cognition. Cross-modal mapping emerges as a particularly promising area for future research, especially in non-human species.