Absence of low-level visual difference between canonical and noncanonical finger-numeral configurations

Canonical finger numeral configurations are named faster than less familiar finger configurations and activate a semantic place-coding representation as symbolic stimuli. However, this does not exclude categorically the possibility that mere visuo-perceptual differences between canonical and noncanonical finger configurations may induce differences in processing speed. This study capitalizes on the fact that, in typical visual-detection tasks, participants focus on low-level visuo-perceptual features to detect a target among distractors sharing the same high-level semantic features, producing the so-called pop-out effect. Participants had to decide whether a canonical finger configuration was present among a set of distractors expressing the same numerosity in a noncanonical way. The results showed that the time needed to detect the presence of the target grew linearly with the number of distractors. This indicates that the canonical target enjoyed no perceptual saliency among the noncanonical configurations (i.e., no pop-out effect) excluding visuo-perceptual differences as the source of the better identification of and semantic access of canonical configurations.