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Anke Huckauf; Binocular coordination when focussing on bright and dark objects. Journal of Vision 2018;18(10):1282. doi: 10.1167/18.10.1282.
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© ARVO (1962-2015); The Authors (2016-present)
Looking at a rouged face gives the impression of more depth of that face. This is thought to be an effect of increased brightness differences between dark and bright parts. Here, the question arises whether such differences affect already basic visual functions like, for example, binocular coordination. Evidence for this assumption can be found in reading literature. Here, there is mixed evidence published on a seemingly different question, namely whether typical binocular coordination during reading results in more crossed (as observed by Nuthmann & Kliegl, 2009) or more uncrossed (e.g., Liversedge, White, Findlay, and Rayner, 2006) fixations. Interestingly, between these studies texts differed in brightness. In three experiments, we investigated the question of whether brightness differences of the text lead to a preponderance of crossed or uncrossed fixations. Binocular coordination was measured via SMI IViewX eye tracker. In Experiment 1, the eyes were calibrated using Gabor patches presented on grey background. When using the same grey background during measurement, there was no change in fixation disparity. However, replicating both earlier findings, reading dark on bright background resulted in more crossed, and reading bright on dark background in more uncrossed fixations. These effects were replicated in Experiment 2 using a bright as well as a dark background for calibration. They were also replicated in Experiment 3 when reading from paper. The data strongly indicate that brightness changes alter binocular coordination. Whereas unsystematic increases of variance might relate to inaccuracies of eye tracking, the replicability of systematic differences in mean vergence across experiments showed that binocular coordination differs for bright and dark objects. This can neither be regarded as an artefact of calibration nor of using a self-illuminating screen. One might further assume that vergence can serve as a measure for distance estimation at near sight.
Meeting abstract presented at VSS 2018
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