Abstract
In the size congruity effect (SCE), participants identify the “smaller” or “larger” digit among pairs of digits more quickly when the physical and numerical size (value) are congruent compared to incongruent. The SCE also occurs in visual search, and suggests that semantic (numerical size) and perceptual (physical size) information interact during visual processing of digits. We examined eye movements to investigate whether semantic and perceptual information interact at an early, perceptual stage of processing, or later, at a decision-related stage. We tracked participants’ gaze as they searched for congruent (e.g., a physically small 2 among large 8s and 9s) or incongruent (e.g., a physically large 2 among small 8s and 9s) target digits and reported their location (right or left side of the display). Early interaction may lead participants to experience conflict prior to attending to the target, resulting in longer time to first fixation (TFF) for incongruent compared to congruent targets. Alternatively, if interference occurs at a decision stage, participants may initially fixate on the target equally quickly (similar TFF) across conditions and experience conflict in incongruent trials only after attending to the target, leading to longer duration or number of fixations to incongruent targets. Results replicated the SCE in visual search and revealed longer TFF for incongruent compared to congruent targets, but no difference in the total duration of fixation or number of fixations on the target across conditions. These findings may be consistent with an early interference account; however, more fixations on distractor items on incongruent trials may have led to longer TFF due to conflict occurring during decisions to reject those distractors prior to fixation on the target. Follow-up work will explore the role of attention to distractors in this task and related implications for early vs. late interaction between physical and numerical size.