Spatial biases in Arithmetic: The Effect of Operation Order and Visual Spacing on Calculations

Visual layout is known to affect computational performance, yet its relationship to testing format and numerical proficiency remains unclear. This preregistered study examined how spatial presentation format affects arithmetic reasoning. We conceptually replicated Experiment 3 of Landy and Goldstone's (2010) study using the Precedence and Proximity Task in a forced-choice format. Additionally, we assessed arithmetic fluency using a speeded test. A total of 201 adults solved 200 mixed addition–multiplication expressions. Spatial congruency was manipulated by varying spacing of addition and multiplication problems so that grouping cues aligned or conflicted with the order-of-operations rules. Operation Order was also manipulated. Participants were faster and more accurate in congruent spacing conditions, whereas incongruent spacing increased operation-order errors, especially when problems began with addition. A group of outliers showed very high accuracy in congruent conditions but extremely high error rates in incongruent ones, suggesting a prepotent susceptibility to perceptual grouping in some individuals. The spacing effect emerged despite differences in task format and response procedure compared to the original study, supporting its robustness. Higher arithmetic fluency was associated with higher accuracy and shorter reaction times. These findings corroborate that visuospatial layout biases symbolic computation and that individuals differ in their susceptibility to it.