Transient covert attention and the perceived rate of flicker.

Transient covert attention affects basic visual dimensions such as contrast sensitivity, spatial resolution, and temporal resolution. Two recent studies provide evidence of corresponding phenomenological changes: The increase in contrast sensitivity and spatial resolution at the attended location is associated with increased apparent contrast (M. Carrasco, S. Ling, & S. Read, 2004) and apparent spatial frequency (J. Gobell & M. Carrasco, 2005). Here, we assessed a phenomenological correlate of attention for temporal vision, asking whether and how transient attention affects perceived flicker rate. We employed a psychophysical method developed to assess changes in appearance by manipulating transient attention via uninformative spatial cues. In each trial, two suprathreshold Gabor stimuli, appearing briefly to the left and right of fixation, were counterphase modulated at either the same or different temporal frequencies. To assess appearance, we asked observers to perform an orientation discrimination task contingent on perceived flicker rate: "What was the orientation of the Gabor that flickered faster?" Results indicated that perceived flicker rate increased at the cued location. A control experiment, in which observers reported the orientation of the Gabor that flickered slower, ruled out a cue bias explanation. We conclude that transient attention increases perceived flicker rate.