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TWK: 8th Tübingen Perception Conference
25th - 27th Feb 2005
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Contrast Effects Between Concurrently Perceiveing and Producing Events
Marc Grosjean (MPI for Human Cognitive and Brain Sciences, München)
The simultaneous perception and production of events has recently been shown to lead to a bi-directional suppression (as opposed to an assimilation) between what is perceived and what is produced. For example, producing a medium-amplitude movement trajectory while concurrently watching a large-amplitude motion trajectory leads to a reduction in size of the produced movement, whereas the size of the large-amplitude motion is perceived as larger than it really is [1]. These perception-action interactions were further investigated here by asking participants to produce movements on a graphics tablet while concurrently perceiving a functionally unrelated motion on a screen. Both the produced movements and the motions presented on the screen could vary in direction. As was expected, the results revealed that the perception of motion direction and the direction of movement production mutually shifted away from each other along the orientation dimension. However, in terms of production, the CE was actually preceded within a given action by an assimilation effect and was only obtained when the overlapping dimension between the perceived and produced events was task relevant. In terms of perception, the CE did not depend on the angular distance between the produced and perceived direction, but did depend on the categorization of the produced movement (e.g., right vs. left). Finally, when both types of CEs were obtained in the same task, their sizes were uncorrelated across participants. Taken together, these results suggest that the CE on production might be, at least in part, strategic in origin and that the source of the two types of CEs may actually differ. The implications of these findings for modeling within the framework of common coding and that of internal forward models will be discussed.
[1] Schubö, Aschersleben, & Prinz, 2001
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