UC Santa Barbara

In mental rotation tasks (MRT), people show a remarkably different pattern of responses to hand stimuli compared to geometric 3D objects. However, the mechanisms of these effects remain unclear. In order to provide a more solid understanding of the cognitive processes involved in the mental rotation of hands, I tested both left-handed and right-handed subjects on a modified Shepard & Metzler task with hand stimuli. I crossed two orthogonal hypothesis axes to yield four competing hypotheses. One axis of the hypothesis space contrasted i) embodied experience (people’s experience with their own hands) versus ii) world knowledge of a right-handed world. The other hypothesis axis contrasted a) the holistic motor imagery matching between the visual image of a hand on the screen and one’s own hand versus b) the resemblance of only the shape outline information from the hand stimuli with the proprioception of one’s own hands. The results suggest that, for mixed-handed people, embodied experience is important in the mental rotation of hands and the information is likely processed through a visual-proprioceptive integration cognitive mechanism. However, for extreme-handed people, the results only showed that extreme right-handers had overall better performance than extreme left-handers. World knowledge might independently influence performance for left hand stimuli while the performance for right hand stimuli is influenced by a combination of world knowledge and embodied experience. Finally, I discuss potential future studies that could further test embodied experience versus world knowledge in left-handed and right-handed people.