Hypothesis
Seeing a small number would speed detection of left-side targets and a large number right-side targets, as Fischer et al. (2003, Experiment 2) reported.
What failed
In a registered replication with 1,105 participants at 17 labs and four interstimulus intervals, the effect was in the original direction only half the time (proportion .50); effects within and across labs were minuscule and incompatible with the original. Finger counting, reading direction, handedness and maths fluency or anxiety did not moderate it.
Broken assumption
Merely seeing a number shifts spatial attention along a mental number line.
Why
The authors conclude the effect failed to replicate and cannot support strong claims about a link between number and space.
From the published paper: Colling et al. Advances in Methods and Practices in Psychological Science, 2020. ↗CC BY