Presentation of numerical uncertainty modulates duration judgments.

The processing of mental magnitudes like space, time, and numbers is thought to be processed in the same brain region. Therefore, the presence of one magnitude dimension would interfere with the processing of another magnitude dimension. Such cross-dimensional interferences have been studied, and most behavioural findings support the idea of a common magnitude system. However, a growing body of literature provides evidence against a generalised representation and argues that cross-dimensional magnitude interferences result due to attention and memory mechanisms. In this study, we manipulated the predictability of the presentation of “large” and “small” numerical magnitudes by presenting them in either a Blocked or Random manner and studied its effect on temporal judgements. In the blocked presentation, “small” and “large” numerical magnitudes were presented in separate blocks, ensuring predictability of the upcoming magnitude on each trial. In the random presentation, these magnitudes were intermixed within a single block, resulting an unpredictability of upcoming magnitude for each trial. Assuming the shared magnitude representation, we hypothesized that the numerical magnitude would affect the duration processing irrespective of how numerals are presented. Our results suggest that numerical magnitude influences temporal judgments only when magnitudes were presented in an unpredictable manner, but not when in a predictable format. These findings suggest that magnitude-related effects on duration judgment may be modulated by attentional mechanisms allocated differently across the two presentation formats rather than a common magnitude system. Our findings highlight how simple magnitude presentation modulates (via attentional mechanism) cross-dimensional magnitude interactions.