Fig. 3: Eye movement patterns in goal-directed and non-goal-directed conditions.

Frequency (a, number of eye movements per second with a radial eye velocity greater than 30 deg/s and amplitude greater than 0.35 visual degrees) and amplitude (b, in visual degrees) of saccades performed during the presentation of videos depicting goal-directed (Grasping Hand condition, in red) and non-goal-directed actions (Empty Hand condition, in orange). No differences between conditions emerged using Wilcoxon signed rank test (in both cases, p > 0.6). c, d represent the proportion of time spent observing a window of 3 visual degrees centered on the hand or target, respectively. This proportion is reported for the two experimental conditions (Empty Hand, in orange, and Grasping Hand, in red) across the four epochs (pre-hand, reaching, withdrawing and post-hand). Post-hoc comparisons with Bonferroni correction showed a significant difference between the two experimental conditions during the withdrawing phase regarding the visual window centered on the hand (c) and during reaching for the visual window centered on the target (d). Asterisks indicate such significant differences: *p < 0.05. Black lines and squares represent median and mean of the group respectively; black dots represent individual scores. Bars on bottom and top of the boxes represent the first and third quartile respectively.