The impact of perceptual diversity in numerical discrimination

The ability to abstract the numerosity of a set, independent of perceptual attributes such as color, shape, or texture, is critical to a true understanding of number. Substantial evidence suggests that variations in perceptual attributes of sets (e.g., differing colors and shapes of items) hinder preschoolers' abilities to exactly match the number of items across sets. Yet, it is unclear whether it is the precise nature of the demands of a matching task that may highlight perceptual attributes of items within the set. Less work has focused on how perceptual variations influence approximate (i.e., imprecise) numerical abilities, such as numerical discrimination. In the present study, 3-10-year-old children and adults were asked to compare sets of items with different perceptual attributes either within the set (e.g., sets containing both blue and red items), across the set pairs (e.g., comparing a set of red items to a set of blue items), or both. Results reveal discriminations through early childhood and adulthood were impaired when perceptual characteristics differed across the sets but not when these variations occurred within the sets themselves. These findings suggest that perceptual variability impacts approximate numerosity judgments, hinting at the processes involved in numerical discrimination.