Moxuan Liu¹, Stella F. Lourenco¹; ¹Emory University

That people readily perceive the number of objects in visual displays is uncontroversial. How number is perceived, however, remains the topic of ongoing debate, particularly the question of whether or not number is perceived independently of other (co-occurring) magnitude dimensions such as cumulative area (i.e., the total area of a set of objects). Some researchers argue that the influence of area on number judgments reflects post-perceptual "late-stage" decision-making. Others, however, have proposed that the relation between number and area may be perceptual in nature. To delineate between these two perspectives, we tested adult participants on a (delayed) match-to-sample task (DMTS, N = 39) designed to rule out decision-stage effects. Participants were instructed to select the choice display (from two options) that matched the sample display in number. Choice stimuli varied in either area or luminance, with differences between area and luminance matched for difficulty (confirmed by a separate group of participants, N = 39). Analyses of participants’ responses (choices and RTs) on the DMTS task revealed greater interference by area than luminance on number matching, despite identical task demands for area and luminance conditions. This finding suggests that the relation between number and area is not simply due to task-based decision-making. To rule out an alternative explanation based on perceptual salience, a subsequent experiment with a triplet odd-one-out task was conducted (N = 24). Analyses revealed variation in the salience of area relative to luminance. Yet there was still greater interference by area than luminance on the DMTS task when area and luminance were comparable in salience. Altogether, our findings suggest that the perception of number is not independent of area information within visual displays. They also raise questions about the nature of the relations between number and other visual attributes such as luminance.