Abstract
In color constancy experiments, observers typically judge surface appearance across an illumination change. Performance in such tasks can be modulated by experimental instructions (e.g., Arend & Reeves, 1986), but the nature of the processes mediating these instructional effects remains unclear. We ask whether eye movements made during a color appearance task provide insight into the underlying processing. On each trial, observers fixated on a color target (3.1° square) presented against a colored background. The background consisted of a simulation of many small illuminated Munsell papers. After one second, the target was replaced by four comparison squares, each 3.1° and located 8.2° eccentric from the fixation point. On illuminant-change trials, the simulated illuminant of the background changed when the comparison squares were presented. On control trials the background remained constant throughout the trial. Three observers were instructed to choose the comparison square from which the light reaching their eye was most similar to the target (spectral-match instructions). Four different observers were instructed to choose the square that appeared to be cut from the same piece of paper as the target (reflectance-match instructions). Observers used a mouse to click on a chosen square. The comparison squares always included both a spectral match and a reflectance match to the target. Observer eye movements were monitored. On the illuminant-change trials, five observers tended to choose the spectral match, and this choice correlated with the comparison square to which they first fixated. Two observers, both of whom were given reflectance-match instructions, tended to choose the reflectance match on most illuminant-change trails. Interestingly, these observers initially often fixated on the spectral match, but during the trial looked increasingly at the reflectance match. We tentatively interpret this dissociation between initial fixation and final choice as revealing an inter-observer difference in the processing used to accomplish the task.
Meeting abstract presented at VSS 2012