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Ryan Langridge, Jonathan Marotta; Moving Targets: Effects of Occlusion on Eye and Grasp Movements. Journal of Vision 2016;16(12):454. doi: 10.1167/16.12.454.
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© ARVO (1962-2015); The Authors (2016-present)
When interacting with our environment, visual information provided by objects we intend to grasp is not always consistent or readily available. This is especially true concerning moving objects, which have the potential to become occluded by larger, closer objects. This study involved participants making pantomimed grasps toward horizontally translating computer-generated targets that were either visible throughout the trial or appeared to move behind an occluding object during travel. The presence of additional computer generated blocks along the top and bottom of the screen was manipulated to test for an effect of increased allocentric information on visual pursuit and grasp accuracy. Eye movement and grasp kinematics were monitored. Results indicate that participants executed more accurately placed grasps and were better able to visually pursue the target with visual feedback than without. Smooth pursuit eye movements were achieved while the target was visible. Once the target encountered the occluder, fixation was maintained until complete occlusion, after which saccades were used to reproduce target movement. Gaze analysis indicated that participants were able to efficiently pursue occluded targets prior to being cued to execute the reach. However, when grasps were made towards occluded targets, the locations of the final gaze and index finger placement were significantly displaced from the target's horizontal position, suggesting that position error occurs during the reach. Surprisingly, the presence of additional cues appeared to have minimal influence on gaze or grasp accuracy, and even impaired accuracy for rightward moving occluded targets. Additionally, cue presence was associated with a gaze position closer to the top edge of the target at the time of grasp. These results indicate impaired performance when visually pursuing and grasping for occluded targets, and specifically highlight the reach component as contributing to position error. Further research is required to understand what differentiates a 'cue' from a 'distractor.'
Meeting abstract presented at VSS 2016
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