Abstract
Background: How does attention affect appearance? Transient covert attention has been shown to increase apparent contrast (Carrasco, Ling & Read, 2003) and apparent spatial frequency (Gobell & Carrasco, 2004). Previous results suggest that attention may affect the appearance of color saturation as well (e.g., Blaser & Sperling, 1999). In the present study, we implemented a psychophysical paradigm to directly assess the effects of transient attention on the subjective appearance of color saturation. Method: Observers were presented with either a peripheral cue (a small circle flashed adjacent to the stimulus location to elicit transient covert attention) or a neutral cue (a small circle flashed at fixation) for 40 ms. Following a 60 ms ISI, paired targets (elongated Gaussian blobs) of identical hue (primary red or primary green) and luminance were presented at 4° eccentricity on either side of fixation. One of the blobs was always presented at a fixed saturation (Standard), while the other blob's (Test) saturation was randomly sampled from a symmetrical range around the Standard saturation. The stimuli were tilted 45° to the left or right. Observers were asked to report the orientation of the target that appeared more saturated (i.e., “redder” or “greener”). We assessed appearance by determining which of the blobs observers reported as appearing higher in saturation. Trials were randomized by test target position (right/left), saturation, hue, orientation, and cue condition. Results & Conclusion: We observed a shift in the point of subjective equality (PSE) with attention. Cueing the Test stimulus reduced the Test saturation required to match the Standard. Likewise, cueing the Standard increased the Test saturation needed to match the Standard. Consistent with the effect of transient attention on early vision, the results indicate that transient covert attention increases apparent color saturation at the attended location.
Grant BCS-9910734/HCP from the National Science Foundation