Space-magnitude associations modulate the familiar-size stroop effect in visual size judgments

The familiar-size Stroop effect shows how prior knowledge of an object’s real-world size influences visual size judgments, slowing reactions when familiar and visual sizes conflict. This study examined how space-magnitude associations, specifically mental number line (MNL) compatibility, interact with Stroop congruency. Participants compared the visual sizes of two objects, ignoring real-world sizes, and identified either the smaller or the larger object across four conditions: Stroop-congruent/MNL-compatible, Stroop-congruent/MNL-incompatible, Stroop-incongruent/MNL-compatible, and Stroop-incongruent/MNL-incompatible. Tasks followed small-then-large or large-then-small identification sequences. Results showed MNL compatibility modulates Stroop interference: MNL-compatible (small-left, large-right) presentations reduced interference, while MNL-incompatible (large-left, small-right) presentations increased it, depending on task type and order. RT distribution analyses revealed MNL effects emerged in slower bins for Stroop-congruent trials and faster bins for Stroop-incongruent trials within small-then-large sequences. These findings suggest that space-magnitude associations shape the familiar-size Stroop effect, revealing a complex relationship between spatial and conceptual representations in size judgment.