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Andrew E. Welchman, Julie M. Harris; Task demands and binocular eye movements. Journal of Vision 2003;3(11):15. doi: 10.1167/3.11.15.
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Humans make rapid movements of their eyes several times a second that enable them to examine objects located at different positions in space with both of their eyes. Much of our understanding of these binocular movements comes from studies using experienced observers performing repetitive, unnatural tasks. But what eye movements are made when naïve observers perform tasks demanding specific binocular visual information? We examined the binocular eye movements produced by observers performing two tasks differing in the visual information needed for their completion. Our motivation for doing this was to examine the role and function of binocular eye movements when making decisions. We considered the fixation strategies adopted by observers, the effects of the task on the dynamics of saccadic eye movements, and the combination of vergence and version in gaze shifts. We report that the task-dependent use of visual information can have a strong influence on the patterns of fixations, whilst not influencing saccade dynamics. Our data provide some support for the notion that observers choose and fixate a notional reference point in the scene when making judgments about depth structure.
Fixation durations were defined as periods between gaze changes or gaze adjustments.
We used the mean duration of gaze on the central patch as a baseline to calculate the relative proportion (ratio) of fixation durations at the other patches (e.g., mean left duration divided by mean center duration).
Data show the number of instances in which the change of vergence associated with a saccade was < 0.2 deg for all saccades made between stimulus patches that necessitated a change of vergence. We chose < 0.2 deg as our isovergence criterion because this was the vergence resolution of the eye tracker that we employed. Data presented in this table differ from those in Figure 4 because those data also included saccades made between stimulus patches requiring the same vergence angle.
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