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Michael Cinelli, William Warren; Eyes or head: Which has the greatest effect on steering control?. Journal of Vision 2009;9(8):1122. doi: https://doi.org/10.1167/9.8.1122.
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© ARVO (1962-2015); The Authors (2016-present)
Do walkers follow their eyes or their heads? Our previous studies of goal-directed walking found that an active head turn toward a target light produced a small path deviation (4%, ~6cm) in the direction of the head turn. In contrast, an active head turn in response to a verbal cue produced a comparable deviation in the opposite direction. The former result appears to be due to attentional capture, whereas the latter may reflect a compensatory mechanism.
Here we ask whether path deviations depend on the head turn, a gaze shift, or both together, and we record eye movements. To dissociate the head and eyes, we tested the following conditions during goal-directed walking: (a) active head turn towards a target light, with free eyes; (b) active head turn in response to a verbal command, with free eyes; (c) active head turn in response to a verbal command, while maintaining fixation on the locomotor goal; (d) saccade in response to a verbal command, while keeping the head facing the locomotor goal; and (e) active head turn and gaze shift in response to a verbal command. Eye movements were recorded with an ASL MobileEye tracker, and head and body movements with an Optotrak.
There were three main results. First, the largest path deviation was again produced by an active head turn in the direction of a target light, with gaze free (~8cm). Second, an active head turn in response to a verbal command produced similar deviations opposite the head with or without an accompanying gaze shift. Third, an active gaze shift without an accompanying head turn did not yield any path deviations. These findings suggest that small path deviations may be due to head turns, not gaze shifts, and are largest when driven by attentional capture.
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