Action induction due to visual perception of linear motion in depth.

Visually perceived motion can affect observers' motor control in such a way that an intended action can be activated automatically when it contains similar spatial features. So far, effects have been mostly demonstrated with simple displays where objects were moving in a two-dimensional plane. However, almost all actions we perform and visually perceive in everyday life are much more complex and take place in three-dimensional space. The purpose of this study was to examine action inductions due to visual perception of motion in depth. Therefore, we conducted two Simon experiments where subjects were presented with video displays of a sphere (simple displays, experiment 1) and a real person (complex displays, experiment 2) moving in depth. In both experiments, motion direction towards and away from the observer served as task irrelevant information whereas a color change in the video served as relevant information to choose the correct response (close or far positioned response key). The results show that subjects reacted faster when motion direction of the dynamic stimulus was corresponding to the spatial position of the demanded response. In conclusion, this direction-based Simon effect is modulated by spatial position information, higher sensitivity of our visual system for looming objects, and a high salience of objects being on a collision course.