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Kelly Chajka, Elia Vecellio, Mary Hayhoe, Barbara Gillam; The role of binocular vision in navigating obstacles. Journal of Vision 2007;7(9):119. doi: https://doi.org/10.1167/7.9.119.
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© ARVO (1962-2015); The Authors (2016-present)
Despite a wealth of knowledge about stereoscopic vision, little is known about the role of stereopsis in the control of everyday actions. Work by Patla et al. (Exp Brain Res, 2002) has shown that when stepping over obstacles, foot position is elevated when only monocular vision is available. Our investigation compared monocular and binocular vision when walking over and around obstacles, and also tracked eye movements during the task. Eye movements were recorded from 8 subjects using an RIT wearable eye tracker (ETRA, Babcock & Pelz, 2004). Subjects stepped over two boxes, walked around a table, and returned to the starting point. Subjects performed two monocular and two binocular trials, with the order counterbalanced across subjects. Subjects were overall 11% slower in the monocular condition (600 ms slower around the table, 500 ms slower stepping over obstacles), and elevated the foot approximately 2 cm higher when stepping over obstacles. Fixations on the obstacles accounted for 30% of total gaze duration in each trial, with remaining fixations falling on the floor or wall. However, eye movement patterns were fundamentally different in monocular versus binocular trials. Subjects fixated longer on obstacles (approximately 150–200 ms per obstacle) in monocular vision. In the monocular condition, they also maintained fixation on the floor in order to guide foot placement between the boxes with high frequency (60%), but did this less often in the binocular case (15%). Thus both eye movements and obstacle avoidance are significantly altered when only monocular cues are available. These findings are consistent with increased uncertainty about spatial configuration in monocular vision, resulting from the loss of either stereopsis or other binocular cues.
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