Number is not just an illusion: Discrete numerosity is encoded independently from perceived size

Abstract

While seminal theories suggest that nonsymbolic visual numerosity is mainly extracted from segmented items, more recent views advocate that numerosity cannot be processed independently of nonnumeric continuous features confounded with the numerical set (i.e., such as the density, the convex hull, etc.). To disentangle these accounts, here we employed two different visual illusions presented in isolation or in a merged condition (e.g., combining the effects of the two illusions). In particular, in a number comparison task, we concurrently manipulated both the perceived object segmentation by connecting items with Kanizsa-like illusory lines, and the perceived convex-hull/density of the set by embedding the stimuli in a Ponzo illusion context, keeping constant other low-level features. In Experiment 1, the two illusions were manipulated in a compatible direction (i.e., both triggering numerical underestimation), whereas in Experiment 2 they were manipulated in an incompatible direction (i.e., with the Ponzo illusion triggering numerical overestimation and the Kanizsa illusion numerical underestimation). Results from psychometric functions showed that, in the merged condition, the biases of each illusion summated (i.e., largest underestimation as compared with the conditions in which illusions were presented in isolation) in Experiment 1, while they averaged and competed against each other in Experiment 2. These findings suggest that discrete nonsymbolic numerosity can be extracted independently from continuous magnitudes. They also point to the need of more comprehensive theoretical views accounting for the operations by which both discrete elements and continuous variables are computed and integrated by the visual system.

Is the approximate number system capacity limited? Extended display duration does not increase the limits of linear number estimation.

“…Rather than reflecting an ANS in the superdigital range, these data support the weaker hypothesis that correlates of numbers beyond 20 can be extracted intelligently (Gebuis et al, 2016), but do not approximate their true numbers. Most studies that support the idea of object units for discrete number have tested arrays exclusively in the range below 20 (e.g., Adriano et al, 2021Adriano et al, , 2022.…”

Exploring Sex Differences in Numerosity Perception Using Dynamic Visual Stimuli: Insights into Cognitive Processing and STEM

“…The object tracking system (OTS), which is responsible for identifying sets of up to four elements, while the approximate numbering system (ANS) is used when the set size exceeds four elements [18]. However, a key research challenge is analyzing the relevant visual tools and sensory features used by the ANS to derive an approximate numerical representation [19]. A distinct ANS trait evidenced in literature is that confidence in the number of objects presented decreases correspondingly with an increase in the actual number [20].…”