Abstract
Background: Selective attention enhances visual information processing, as measured by behavioral performance and neural activity. However, little is known about the effects of attention on subjective experience. Here we studied the effect of transient (exogenous) attention - automatic and short-duration preferential processing at a given location - on the subjective appearance of visual motion, using a psychophysical procedure that directly measures appearance and controls for response bias (Carrasco, Ling & Read, 2004).
Method: Observers viewed briefly presented (150 ms) pairs of dot patterns (5° diameter, 8° eccentricity on the horizontal meridian), and reported the motion direction of the more coherent pattern. In each trial, one pattern had 50% coherence and the other varied randomly between 10% and 90%. Uninformative peripheral cues presented 80 ms before stimulus onset directed transient attention to one of the stimulus locations. To rule out response bias, in a control experiment, we increased the time interval between the cue and the stimuli to 450 ms, such that the effect of transient attention would expire before stimulus presentation.
Results: We found that directing attention to a stimulus location increases its perceived coherence level and improves discrimination performance. In the control experiment, the cues had no effect on apparent coherence or discrimination. Our results are consistent with physiological studies showing that attention modulates motion processing and provide evidence of a subjective perceptual correlate of attention with a concomitant effect on performance.