Read, S, Ling, S, & Carrasco,
M (2003). Covert Attention Alters Visual Appearance. Vision Sciences
Society. Sarasota, FL.
Although it has long been established that covert spatial attention improves
performance in a number of visual tasks, there is a long-standing debate
as to whether attention actually alters appearance. When attention is
allocated to a given location via a brief peripheral cue, contrast thresholds
along the psychometric function are decreased for the target (Cameron,
Tai & Carrasco, 2002). From such findings, it has been inferred that attention
actually changes the appearance of an attended stimulus. In this study,
we directly tested whether covert attention alters phenomenological appearance.
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, two Gabor patches of either 2 or 6 cpd appeared for 100 ms
at 4º eccentricity along the horizontal meridian. One of the Gabors was
always presented at 6% contrast (Standard), and the other ranged from
1-12% in contrast (Test). The stimuli were tilted 45º to the left or right.
Observers performed an orientation discrimination task for the Gabor that
they perceived to be of higher contrast. We assessed appearance by determining
which of the Gabor patches observers reported as appearing higher in contrast.
Consistent with previous studies, our results show a threshold shift in
orientation discrimination accuracy across the psychometric function with
attention. The results indicate that attention decreases threshold in
the psychometric function not only in contrast sensitivity, but also in
appearance. Although suggested by past studies, these results show that
visual attention alters the phenomenological appearance of an attended