Figure 1

Experimental stimulus, procedure. (A) Experimental conditions. The visual stimulus consisted of the point-light actions of two agents (interacting and swapped) with two orientations (upright and inverted). In the interacting condition, the two agents interacted with each other. In the swapped condition, the positions of each agent were swapped with each other, thus participants perceived that each agent acted independently. (B) Experimental procedure (an example of Up-Interacting condition). For Stim-1, the scrambled two-agent BM (initial position of point-lights was spatially scrambled) stimulus was presented for 1980 or 2970 ms. For Stim-2, the two-agent BM stimulus was presented for 990 ms. Then, participants were required to judge whether the presented Stim-2 was upright or inverted. Note: to understand the stimulus more easily, the background static dots are not shown here in the Stim-1 and Stim-2 phases. However, in the actual experiment, the background static dots were superimposed on the point-light motion stimulus in both Stim-1 and Stim-2 phases, as shown in (C). Thus participants perceived a point-light animation consisting of white point-light dots. Due to the presence of background static point-light dots, participants could perceive a smooth point-light animation.