Are perceptual judgments dissociated from motor processes? A prism adaptation study

When asked to choose which of two chimeric faces composed of 'smiling' and 'neutral' half-faces is happier, healthy adults select the face in which the left half is smiling. Here, we show that this perceptual leftward bias is associated with a bias in eye movements to the same side. However, when we shifted the pattern of eye movements towards the right side by using prismatic lenses, we did not observe a concurrent shift in the perceptual judgments. Therefore, we argue that overt motor responses are not necessary for perceptual judgments. Furthermore, we argue that while prism adaptation influences performance on motor tasks, it cannot influence higher-order representational processes. (c) 2004 Elsevier B.V. All rights reserved.