The developmental origins of Visual Working Memory and Numerical Acuity: investigating functional independence in 9-12-month-old infants

The first year of life is characterized by the development of fundamental cognitive abilities, including visual working memory (VWM) and numerical acuity (NA). Visual working memory enables the temporary storage and manipulation of visual information, whereas numerical acuity, supported by the approximate number system (ANS), allows individuals to estimate and discriminate quantities without relying on symbolic representations. Although both these abilities are considered evolutionarily ancient and innate abilities that we share with other species, their functional relationship remains poorly understood. Previous research has suggested that visual working memory and numerical acuity are closely related and may rely on overlapping mechanisms. However, Dell’Acqua et al. (2024) demonstrated that these two systems rely on functionally independent mechanisms and are processed differently in adults. But what is the case of infants? If the two processes are functionally independent, we may expect them to have different developmental trajectories. In the present study, we test this hypothesis. Specifically, we assess and correlate approximate number system (ANS) and visual working memory (VWM) abilities in 9–12-month-old infants using a looking-time paradigm. The results showed an overall change preference for the VWM task, although performance varied across set sizes. In contrast, infants showed no evidence for numerical discrimination in the ANS task. We predicted no significant correlations between these abilities, and the results were consistent with this prediction. These findings provide preliminary support for the possibility that the two abilities function relatively independently. By clarifying this developmental relationship, the present study may contribute to a more comprehensive understanding of the developmental foundations of numerical acuity and visual working memory, while providing further insight into the organization and emergence of cognitive systems during the first year of life.