No intrinsic number bias: Evaluating the role of perceptual discriminability in magnitude categorization

Abstract

Accumulating evidence suggests that there is a spontaneous preference for numerical, compared to non‐numerical (e.g., cumulative surface area), information. However, given a paucity of research on the perception of non‐numerical magnitudes, it is unclear whether this preference reflects a specific bias towards number, or a general bias towards the more perceptually discriminable dimension (i.e., number). Here, we found that when the number and area of visual dot displays were matched in mathematical ratio, number was more perceptually discriminable than area in both adults and children. Moreover, both adults and children preferentially categorized these ratio‐matched stimuli based on number, consistent with previous work. However, when number and area were matched in perceptual discriminability, a different pattern of results emerged. In particular, children preferentially categorized stimuli based on area, suggesting that children's previously observed number bias may be due to a mismatch in the perceptual discriminability of number and area, not an intrinsic salience of number. Interestingly, adults continued to categorize the displays on the basis of number. Altogether, these findings suggest a dominant role for area during childhood, refuting the claim that number is inherently and uniquely salient. Yet they also reveal an increased salience of number that emerges over development. Potential explanations for this developmental shift are discussed. Research Highlights Previous work found that children and adults spontaneously categorized dot array stimuli by number, over other magnitudes (e.g., area), suggesting number is uniquely salient. However, here we found that when number and area were matched by ratio, as in prior work, number was significantly more perceptually discriminable than area. When number and area were made equally discriminable (‘perceptually‐matched’), children, contra adults, spontaneously categorized stimuli by area over number (and other non‐numerical magnitudes). These findings suggest that area may be uniquely salient early in childhood, with the previously‐observed number bias not emerging until later in development.

Modeling Magnitude Discrimination: Effects of Internal Precision and Attentional Weighting of Feature Dimensions

“…In our results, number was not consistently the most‐used nontarget feature on other comparisons, and it was the least strongly relied‐upon feature on its own task (compared to the weight on surface area during the surface area task, or the weight on convex hull during the convex hull task). Instead, consistent with recent work indicating that number may not have a privileged role once feature perceptibility is taken into account (Aulet & Lourenco, 2023), these results suggest that number is not more easily focused on when other features conflict with it.…”

A Methodological Framework for Stimuli Control: Insights from Numerical Cognition

“…Recently, Lourenco (2021, 2022) suggested an alternative approach to match the perceptual rather than mathematical discriminability of quantity and surface area. In a numerical comparison task with children (Aulet & Lourenco, 2022), when decimal-scale mathematical ratios were matched, a bias for numerosity over surface area emerged. However, when perceptual discriminability was matched, ensuring changes in quantity were equally easy to discriminate as changes in total surface area, a bias for surface area over numerosity emerged.…”