Abstract
Despite frequent appeals to the ecological relevance of number perception (e.g., for foraging), number perception usually studied using stimuli that differ greatly from real-world scenes: dot array stimuli comprised of homogenous elements, presented on a solid background. Thus, it is unclear how our current understanding of number perception relates to number perception as deployed ‘in the wild.’ In the present study, adult participants completed a number discrimination task with four stimulus conditions: 1) dot arrays, 2) dot arrays with gaussian noise, 3) naturalistic images, and 4) pseudo-naturalistic images, in which the approximate sizes, locations, and colors of the objects in the naturalistic images were preserved, but featural/semantic information was removed. We found that participants were significantly less accurate at discriminating naturalistic and pseudo-naturalistic stimuli than dot arrays (see also, Odic & Oppenheimer, 2023). Furthermore, we found a significant interaction between stimulus condition and the total number of objects presented each trial (summed across both displays), such that for naturalistic and pseudo-naturalistic stimuli only, participants were less accurate on trials with more total objects. Moreover, and critically, within the naturalistic and pseudo-naturalistic conditions, there was a significant interaction between total number of objects and object occlusion, such that the number of objects only impacted performance when stimuli contained occluded (i.e., overlapping) objects. These findings suggest that real-world number discrimination is dependent on object segmentation (Franconceri et al., 2009), and therefore, likely could not originate from low-level processes in subcortical or early visual cortical areas (Fornaciai & Park, 2018).