Figure 4: Effects of deadline-induced speed pressure on pre-motion pupil diameter and evoked pupil dilation.

(a) Effect of speed regime on unbaselined pupil diameter, as measured during the period directly preceding motion onset. Error bars=s.e.m. ***=P<0.001. (b) Evoked pupil dilation separated by speed regime and aligned to both motion onset (left) and response (right). Waveforms are relative to a pre-motion baseline. (c) Response-aligned pupil dilation after sorting trials by RT into 3 equal-sized bins, separately for the FR and DL conditions. (d) Scatterplot illustrating the linear relationships between RT and evoked pupil dilation for each speed regime. Points and error bars are mean±s.e.m. of data that were z-scored within subjects, pooled across subjects and grouped into 20 bins; z-scoring was carried out across speed regimes to preserve main effects of speed emphasis. In c, shaded grey regions show measurement windows for effects shown in d and reported in text.