Apparent motion is less apparent with attention

Can spatial transient attention affect apparent motion? To answer this question we used two different tasks that involved apparent motion displays. The first display was composed of a short line segment appearing successively intwo spatial locations with a varying ISI. The task required observers to rate the quality of motion. The second display included a rectangle composed of small dots. The rectangle also appeared in two spatial locations successively, with a varying ISI, but the order of locations ensured that the rectangle appeared to be moving upward on half the trials and downward on the other trials. Observers were asked to indicate the direction of motion. To manipulate transient attention these two tasks were coupled with peripheral precueing: On the "cued" trials a peripheral cue indicated the location of the apparent motion target prior to its appearance, allowing observers to direct their attention in advance to the target location; on the "neutral" trials a neutral cue specified that the target could appear in any one of the possible locations. In both tasks, the target could appear in one of several locations at the periphery, and stimuli durations ensured that eye movements could not occur between cue onset and target offset. The results indicate, for both tasks, that the perception of motion was weaker when observers attended the target location. Observers gave lower quality rates and were less accurate in judging the direction of motion on the cued than the neutral trials. In addition, there is an indication that the ISI at which motion perception is strongest is longer when observers attend the target location. These findings are consistent with previous findings regarding attentional effects on temporal processes (e.g., lower temporal resolution, longer visible persistence, and longer duration estimation) and can be accounted for by an attentional mechanism that favors parvocellular over magnocellular neurons.