Simone Bosbach

A Simon effect with stationary moving stimuli

To clarify whether motion information per se has a separable influence on action control, the authors investigated whether irrelevant direction of motion of stimuli whose overall position was constant over time would affect manual left-right responses (i.e., reveal a motion-based Simon effect). In Experiments 1 and 2, significant Simon effects were obtained for sine-wave gratings moving in a stationary Gaussian window. In Experiment 3, a direction-based Simon effect with random-dot patterns was replicated, except that the perceived direction of motion was based on the displacement of single elements. Experiments 4 and 5 studied motion-based Simon effects to point-light figures that walked in place--displays requiring high-level analysis of global shape and local motion. Motion-based Simon effects occurred when the displays could be interpreted as an upright human walker, showing that a high-level representation of motion direction mediated the effects. Thus, the present study establishes links between high-level motion perception and action.

Is direction position? Position- and direction-based correspondence effects in tasks with moving stimuli

Five experiments were carried out to test whether (task-irrelevant) motion information provided by a stimulus changing its position over time would affect manual left–right responses. So far, some studies reported direction-based Simon effects whereas others did not. In Experiment 1a, a reliable direction-based effect occurred, which was not modulated by the response mode—that is, by whether participants responded by pressing one of two keys or more dynamically by moving a stylus in a certain direction. Experiments 1a, 1b, and 2 lend support to the idea that observers use the starting position of target motion as a reference for spatial coding. That is, observers might process object motion as a shift of position relative to the starting position and not as directional information. The dominance of relative position coding could also be shown in Experiment 3, in which relative position was pitted against motion direction by presenting a static and dynamic stimulus at the same time. Additionally, we explored the role of eye movements in stimulus–response compatibility and showed in Experiments 1b and 3a that the execution or preparation of saccadic eye movements—as proposed by an attention-shifting account—is not necessary for a Simon effect to occur.

Movement-based compatibility in simple response tasks

Previous studies reported that movement observation affected movement execution. Using one and the same set of responses (i.e., lifting or tapping the finger), correspondence effects were observed for simple responses when the go-signals were similar to the responses (i.e., movies of finger movements) but not when they were dissimilar (i.e., moving squares). The difference was attributed to a higher degree of ideomotor compatibility with visible limb movements. We tried to provide further evidence for ideomotor theory by manipulating the degree to which different responses matched one and the same set of stimuli (drifting sine-wave gratings). To this end, we measured simple reaction time of dynamic (hand movements) or static (key presses) movements in response to the onset of object motion. Object motion and dynamic responses showed ideomotor compatibility without looking alike; however, both stimulus and response involved continuous displacements. Correspondence effects were observed for dynamic responses, but not for static responses.