accurate visuomotor control below the perceptual threshold of size discrimination准确visuomotor控制规模歧视知觉阈值以下.pdfVIP

Accurate Visuomotor Control below the Perceptual Threshold of Size Discrimination 1 1 2 3 Tzvi Ganel *, Erez Freud , Eran Chajut , Daniel Algom 1 Department of Psychology and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel, 2 Department of Education and Psychology, The Open University of Israel, Raanana, Israel, 3 Department of Psychology, Tel-Aviv University, Tel-Aviv, Israel Abstract Background: Human resolution for object size is typically determined by psychophysical methods that are based on conscious perception. In contrast, grasping of the same objects might be less conscious. It is suggested that grasping is mediated by mechanisms other than those mediating conscious perception. In this study, we compared the visual resolution for object size of the visuomotor and the perceptual system. Methodology/Principal Findings: In Experiment 1, participants discriminated the size of pairs of objects once through perceptual judgments and once by grasping movements toward the objects. Notably, the actual size differences were set below the Just Noticeable Difference (JND). We found that grasping trajectories reflected the actual size differences between the objects regardless of the JND. This pattern was observed even in trials in which the perceptual judgments were erroneous. The results of an additional control experiment showed that these findings were not confounded by task demands. Participants were not aware, therefore, that their size discrimination via grasp was veridical. Conclusions/Significance: We conclude that human resolution is not fully tapped by perceptually determined thresholds. Grasping likely exhibits greater r