(a) As compared to the placebo condition (light grey), choline ingestion by the participants (dark grey) improved hit distance to the center of the target (left), slowed down reaction times (center), and decreased the amount of misses for participants that were most accurate (right) (C = choline; P = placebo; Inacc = inaccurate, participants with more misses; Acc = accurate, participants with less misses). (b) Participant’s pupil sizes also decreased as a function of time after choline (dark grey) but not placebo (light grey) supplementation. (c) Changes in pupil size correlated with hit distance to target center (dotted, black), reaction times (dashed), and number of misses (dotted, grey). Error bars represent the mean and standard error across participants (a–b) and asterisks (*p < 0.05, **p <0.01) indicate significance of t-test comparisons between choline and placebo conditions (a–b) or Spearman’s rho correlations between change in pupil size and task behavior (c). As indicated with the shaded area, the motoric aiming task was performed approximately 70–90 minutes after ingestion.