Author response image 1. Motion direction-numerosity adaptation when adapting with small numerosities.
Leftward motion cross-adaptation leads to a stronger overestimation effect than rightward motion adaptation. The scatter plot shows that PSEs for leftward motion were consistently smaller than for rightward motion (mean difference in PSE 15.85 dots; t(9)=4.523, p=0.001, dHedges=1.017, two-sided). This indicates that as when adapting with large numerosities, leftward motion shifts numerosity perception down the number line, while rightwards motion shifts numerosity perception up the number line. A general main effect of static numerosity and/or texture density leading to overestimation independent of motion direction is also evident in a majority of subjects (all data points falling left and/or below the dashed lines).