Figure 1.

Experimental tasks. (A) Action observation task. Example of 1 of 39 possible actions and its control, followed by the task structure. A = action; C = control; Ctrl = control; OBS = observation. The ActionOBS and CtrlOBS videos were grouped in blocks of 7 s. Each block contained three actions from the same condition, with a total of 13 blocks for each condition. Blocks were separated by a fixation cross for a random period of 8–12 s, displayed on a background that was visually similar to the table. (B) Weight discrimination task. Frame extracted from the NoSleeve (top) and Sleeve (bottom) weight lifting condition, followed by the trial structure for the functional MRI (top) and behavioural experiments (bottom). In the functional MRI (fMRI) task the window of time participants were requested to answer was indicated by a weighing scale. In the behavioural task, clips were preceded by the number 1 or 2 denoting whether it was the first or second clip of the pair. The sentence following the video was translated from Dutch for illustration purposes. RT = participant’s reaction time. (C) Kinematic analysis of the weight-lifting videos. Mean ± standard error of the mean (SEM) of the vertical velocity of the forearm as a function of weight relative to the onset of the videos, averaged over the Sleeve and NoSleeve conditions. Moments in which velocity carries significant information about the weight are marked in grey, as revealed by a one-way ANOVA comparing velocity across the three weights at P < 0.01.