Significant interactions in mixed-effects analysis for individual differences measure with interference effects (see Dawson, 2014, for plotting methods). For RTs (a1,a2,b1), the points plotted for low and high capacity subjects are for −1 and +1 standard deviation from the mean on the composite WM measure or semantic STM measure. For error rates (b2), the values of the interference effect size (on x-axis), ranging from (−1.5) to (1.5) standard deviations from the mean, were calculated in 0.25 std units, with a line fitted to these effects. Panels (a1,a2) show the Syntactic interference × WM composite score interaction in self-paced reading time (ms) in the critical region (“will visit”) and the spillover region (“the director”), respectively. Panel (b1) shows the Semantic interference × Category probe interaction in question answering speed. Panel (b2) shows the Semantic interference × WM composite and Semantic interference × Vocabulary interactions in question answering error rates. The scatter plots with data points from each subject are shown in Appendix G in Supplementary Material.