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Brian Keane, Yujia Peng, Docia Demmin, Steven Silverstein, Hongjing Lu; Evidence that low IQ, but not schizophrenia, impairs motion integration. Journal of Vision 2018;18(10):51. doi: https://doi.org/10.1167/18.10.51.
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Background. Prior studies have documented biological motion perception deficits in schizophrenia. Do these deficits arise from poor social cognition, perceptual organization, basic motion processing, or sustained attention? Methods. To address the question, we assessed 24 chronic schizophrenia patients and 27 healthy controls on three motion discrimination tasks: coherent motion, where subjects indicated whether a cloud of dots moved leftward or rightward; dynamic form, where subjects indicated whether a translating, point-dot rectangle was tilted leftward or rightward; and biological motion, where subjects judged whether a human point-light figure walked leftward or rightward. In all cases, task difficulty depended on the directional variability of the background dot motion. Thresholds were determined via an adaptive staircase procedure and corresponded to the amount of variability needed to generate 80% discrimination accuracy. Ten catch trials were additionally provided for each task to ensure that subjects were properly attending to the screen. To remove the possibility of group differences in button press errors, subjects provided verbal rather than button press responses. Results. Surprisingly, patients and controls demonstrated similar thresholds and also near-ceiling catch trial accuracy for all tasks (ps>.1, all ds< .35). Moreover, in all but the coherent motion task, higher IQ correlated with better performance (ps< .001); the effects were not moderated by subject group (ps>.09). Although patients as a whole were moderately symptomatic and disabled, symptom levels did not correlate with performance. Conclusion. These results suggest that schizophrenia patients have intact perception of motion coherence, dynamic form, and biological motion, at least when the experiment requires integrating local motion information to perceive global motion or shape. Prior studies may have identified deficits because of group differences in IQ or motivation, or because of task differences having to do with segmenting signal dots from noise.
Meeting abstract presented at VSS 2018
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