Mental Object Rotation and Egocentric Body Transformation: Two Dissociable Processes?

An important question in studies on mental rotation is the difference between mental object rotation and egocentric body transformation.To test whether these two tasks rely on dissociable mechanisms we tested non-dancers and professional dancers as experts.In both tasks, stimuli rotated in the picture plane (x-axis) and in depth (z-axis) were presented and the participants were engaged in mental rotation tasks.The mental object rotation task (MORT, 3D-cubes used by Shepard & Metzler, 1971) was a same-different task and the mental body transformation task (MBRT, line drawings of human bodies similar to those used by Parsons, 1987) was a left-right decision.We measured response times (RTs) and error rates (ERs) in two randomized blocks.The cubes and body figures were presented in exactly the same rotation conditions; in the picture plane, 0°, 45°, 90°, 135°, and 180°, and in combination with a rotation in depth, 0° (the stimuli are rotated in the picture plane only) and 180°.Moreover, we assessed the participants' imagery abilities with three different questionnaires.In the experimental tasks, we found a linear increase in RT with increasing angle for body figures rotated in the picture plane (back view), for cubes rotated in the picture plane, and for the cubes rotated in the picture plane and in depth.In the MORT it took participants longer to respond to the cubes when they were also rotated in depth except for 180°.The MBRT revealed a different pattern.The RTs were even faster for inverted body figures when they were rotated in depth (front view) compared to when they were rotated in the picture plane only (back view).This finding suggests that participants use different strategies depending on the perceived orientation of the stimulus.The results indicate impaired performance in the MORT for the experts.