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Dagmar Wismeijer, Casper Erkelens, Raymond vanEe, Mark Wexler; Depth cue combination in spontaneous eye movements. Journal of Vision 2010;10(7):76. doi: 10.1167/10.7.76.
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© ARVO (1962-2015); The Authors (2016-present)
Where we look when we scan visual scenes to obtain an understanding of the 3D world around us is a question of interest for both fundamental and applied research. Recently, it has been shown that depth is an important variable in driving eye movements: the directions of saccades tend to follow depth gradients (Wexler (2008), Janssen (2009)). Whether saccades are aligned with a single depth cue or a combination of depth cues is still unknown. And, in the latter case, it is interesting to ask whether saccades are based on similar combination rules as those that apply to depth perception. Moreover, these scanning eye movements across different depth planes are composed of two distinct components: conjugate shifts of gaze (saccades) and disjunctive movements changing the depth of fixation (vergence). And the same questions about the effect of depth cues still apply to vergence: various studies have reported that vergence is guided by the consciously perceived depth percept, whereas others report that vergence is based on depth cue(s). Here we studied what depth information is used to plan both saccades and vergence. We showed observers surfaces inclined in depth, in which perspective and disparity defined different plane orientations (both small (0°-45°) and large (90°,180°) conflicts). Observers' eye movements were recorded binocularly, while they scanned the surface. After the stimulus presentation, observers reported the perceived surface orientation using a joystick. We found saccade directions and perceived surface orientation use the same pattern of depth cue combination: a weighted linear cue combination for small conflicts and cue dominance for large cue conflicts. The weights assigned to each cue varied across subjects, but were strongly correlated for perception and saccades, within subjects. This correlation was maintained while manipulating cue reliability. Vergence on the other hand was dominated by the disparity cue.
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