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Wei-Dong Tao, Jing-Jiang Yan, Peng Wang, Liu Zhou, Hong-Jin Sun; Dissociation of Egocentric and Object-centric processing in mental rotation. Journal of Vision 2007;7(9):931. doi: https://doi.org/10.1167/7.9.931.
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Mental rotation can take either egocentric or object-centric forms. We explored the dissociation of these two processing mechanisms using a special stimulus (hand), which may invoke a mental transformation of either the viewer's own body (hand) or the visual display. In Experiment 1, the stimuli consisted of back view of human hands created by a 3D graphics software. Each picture of the hand was presented at an orientation rotated in lateral or medial direction from the upright orientation. Each participant completed (1) a left or right hand judgment task (LR task) when either a left or right hand picture was presented and (2) a same or different judgment task (SD task) when pictures of two hands were presented. The results showed that in-rotation (rotated medially) hand was recognized more quickly and accurately than out-rotation hand in LR task (in-rotation effect), but not so in SD task. This suggests that the processing of mental rotation in LR task is limited by the biomechanical constraints of the corresponding physical rotation. In Experiment 2, participants responded through a microphone while seated in front of a computer screen with their hands positioned on their laps and the back of their hands faced up. The same patterns of result were observed as in Experiment 1 for both back and palm views of hand stimuli. However, the back view of the hands was recognized more quickly and accurately than the palm view in LR task, but not so for SD task. These results suggest participants use different spatial transformation mechanisms in LR (egocentric) and SD (object-centric) task. It appears that both the material of the body parts and paradigms of mental rotation determine the reference frame participants adopted and the in-rotation effect might serve as indicator for the dissociation of egocentric and object-centric mental rotation.
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