Figure 1

Example of a trial within one of the experimental blocks. Each block began with a fixation point for 1000 ms, followed by the instruction(in the single-task condition: ‘watch the movie’, in the dual-task condition ‘watch the movie and count backward’); then the video clip started with a frame showing the actor’s face holding a neutral expression. By the 3th second, the camera zoomed in on the actor’s hand, which was then touched alternatively by a rubber eraser (neutral stimulus), or by a needle (harmful stimulus), then within 4000 ms, participants were instructed to explicitly judge the painful experience of the actor using a Likert scale from 1 (not painful at all) to 9 (highly painful) by pressing an appropriate key on the number pad with their dominant hand. This sequence (within the dashed-line rectangle) was repeated six times per block; the experimental blocks were separated by a 2-minute interval during which participants were asked to watch a relaxing video clip.