Directional spatial–numerical associations in magnitude comparison: The role of response setup [Author Accepted Manuscript]

The present study examined whether the response setup influences the expression of directional spatial–numerical associations (SNAs) in a magnitude comparison task. Participants selected either the smaller or the larger number from pairs of digits presented simultaneously. Experiment 1 used a unimanual response setup, with left and right responses made by different fingers of the same hand, whereas Experiment 2 used a bimanual response setup, with left and right responses distributed across the two hands. Directional SNAs were assessed using two complementary indices: a stimulus-arrangement compatibility index and a response-mapping index. The former assessed whether responses were facilitated when the smaller digit appeared on the left and the larger digit on the right, whereas the latter assessed whether small pairs were associated with faster left responses and large pairs with faster right responses. Across both experiments, the stimulus-arrangement compatibility index provided no evidence for a directional SNA. In contrast, the response-mapping index revealed a left-to-right SNA in Experiment 2, but only in the task in which participants responded to the smaller number. Robust numerical distance effects were observed across tasks. Exploratory cross-experiment analyses further showed that overall response speed varied as a function of both response setup and task, whereas the numerical distance effect varied by task but not by response setup. These findings suggest that directional spatial coding in magnitude comparison is sensitive to how left–right responses are implemented, whereas distance-related magnitude processing is robust across response setups but modulated by task instruction.