Figure 1.

Experimental layout. The two computers were connected via parallel port. The situation depicts an instruction block in the single effect group: The right participant performs key presses always triggering his “own” effect, here the red life buoy, while the left participant watches. Earlier the right participant had watched the left participant triggering her “own” effect, the yellow life buoy. After the instruction phase each participant performed the task on his/her computer separated by the divider wall. Throughout experimental trials both participants wore headphones delivering white noise to ensure they did not hear button presses.