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Matteo Toscani, Matteo Valsecchi, Karl Gegenfurtner; Where we look determines what we see. Journal of Vision 2011;11(11):346. doi: https://doi.org/10.1167/11.11.346.
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It is not yet clear how we form a global impression of the colorimetric properties of real objects. Giesel & Gegenfurtner (2010, Journal of Vision) found that lightness matches were higher than the mean lightness of objects. Here, we investigated whether this effect could be due to observers fixating at the more salient bright parts of the objects. Observers had to adjust the color of a uniform spot of light to the color of one of six objects (three candles, a paper cone, a wool ball and a wool cylinder). Eye movements were measured with an EyeLink II system while the observers performed the task. We replicated the earlier results by Giesel & Gegenfurtner (2010). We also observed that the matched lightness was similar to that of the most frequently fixated object regions, as observers tended to fixate points with above-average lightness. In order to investigate a possible causal link between fixations and color matches, we forced participants to fixate a specific point on the image. This was achieved in a gaze-contingent display by having the image disappear when observers attempted to fixate other points. The matched luminance was higher when observers were forced to fixate in a bright region of the image than when they fixated a dark region. We excluded a possible role of adaptation by forcing observers to match the object color with a test box in a non adapted retinal area. We can thus conclude that the way we perceive the color of objects is driven by the way we look at them, as had been suggested earlier (Kuriki, 2004, Optical Review; Cornelissen & Brenner, 1995, Vision Research). More specifically, objects appear brighter when we look at their brighter side. As a side effect, this leads to more accurate lightness matches that are invariant of object geometry.
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