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Jillian Nguyen, Robert Isenhower, Polina Yanovich, Jay Ravaliya, Thomas Papathomas, Elizabeth Torres; Quantifying changes in the kinesthetic percept under a 3D perspective visual illusion. Journal of Vision 2013;13(9):779. doi: 10.1167/13.9.779.
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© ARVO (1962-2015); The Authors (2016-present)
OBJECTIVE: To explore how reaches toward a target embedded in 3D scenes are affected by top-down and bottom-up signals when participants perform the task at their comfort pace or at instructed slow/fast speeds.
METHODS: Two 3D stimuli: (1) A proper ("forced") perspective, where the perspective-painted cues are congruent with bottom-up signals (binocular disparity, motion parallax, etc.). (2) A reverse-perspective, where the painted cues compete with bottom-up signals, thus eliciting bistable percepts of (a) veridical depth or (b) illusory reverse-depth; the illusion affects perceived 3D surfaces orientations drastically. Under binocular viewing conditions, subjects viewed the stimuli and grabbed at planar disk targets at their own set pace or at fast or slow speeds as instructed, while we recorded their full motor response from initiation of movement towards the target to the hand retraction to resting position.
RESULTS: For reaches performed under comfort speeds, the curvature and length of hand-path trajectories were significantly affected by the illusion. Reaches performed under the veridical percept differed markedly from reaches under the illusory and the proper percepts. Trajectories under illusory and proper percepts were strikingly similar. Additionally, this held true both in the goal-directed movement towards the target and in the spontaneous hand retraction. When speed instructions were added, reaches under the illusory percept did not statistically differ from either the veridical percept or the proper percept.
CONCLUSIONS: Overall we find compelling evidence that top-down visual processes affect both our visual and our kinesthetic percepts. The interactions between the illusory percept and the commanded speed strongly manifested in the retraction movements, which ceased to be spontaneous and turned more deliberate, despite lack of instructions regarding their performance. We discuss our results in the context of deliberate and automatic mental processes that take place during motor decisions and program selection in the face of sensory-motor noise.
Meeting abstract presented at VSS 2013
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