Sharpening the number sense: Developmental trends in numerosity perception

Numerosity perception, the ability to process and estimate the number of objects in a set without explicitly counting, has been widely studied, and one well-established finding is that children become more accurate at perceiving numerosity with age. The question remains, however, what the underlying cognitive processes and mechanisms are that drive this improvement. Some authors have suggested that this is due to an increased numerical precision (i.e., the sharpening hypothesis), whereas others have proposed that the more accurate performance is due to the improved ability to inhibit non-numerical features of the display such as object size and spacing of items (i.e., the filtering hypothesis). The current study examined the developmental trajectory of numerosity perception across three age groups (M = 5.65, M = 11.03, and M = 20.10 years). As expected, more accurate performance was observed with age. Regression and analyses of variance revealing the contribution of numerical and non-numerical predictors in performance show that the performance in all age groups was primarily driven by numerical information and that its contribution increased with age. In addition, a consistent bias toward non-numerical features was observed in all age groups. These results support the sharpening hypothesis for children from 5 years of age to early adulthood, suggesting that from this age onward children increasingly focus on numerical information as they get older. These results have important implications for the understanding of the development and specific improvements of numerical perception.