Combined effects of feature-based working memory and feature-based attention on the perception of visual motion direction.

We investigated whether human subjects' ability to identify the direction of a brief pulse of coherent motion in a random-dot pattern (RDP) was influenced by: (a) maintaining in working memory the direction of motion of an RDP previously presented far from the pulse (feature-based working memory or FBWM, Experiment 1), (b) attending to the direction of an RDP co-occurring with but far from the pulse (feature-based attention or FBA, Experiment 2), and (c) both FBWM and FBA acting simultaneously (Experiment 3). In the first two experiments, pulse direction identification performance was higher when the remembered direction (FBWM) or the direction of the concurrently attended RDP (FBA) matched the pulse direction than when it was opposite. In Experiment 3, performance was highest when both the remembered and the attended directions matched the pulse direction (combined effects of FBWM and FBA), it was intermediate when only one of them matched the pulse direction, and it was lowest when neither matched the pulse direction. Our results demonstrate that both feature-based working memory and feature-based attention can individually modulate the perception of motion direction and that when acting together they produce an even larger modulation.