Influence of crowd behaviour on estimates of biological motion speed

Does the behaviour of to-be-ignored “crowds” influence the perception of target walker speed? Baseline trials presented two point-light walkers that moved at different speeds. The task was to report whether the red or green walker was faster. On experimental trials, the task was the same, but targets were surrounded by 5 red and 5 green figures that made two task-irrelevant crowds. On speed-congruent trials, the faster target had a colour-consistent crowd that moved at an even faster pace. On speed-incongruent trials, the colour-consistent crowd moved at a slower pace. There were three possible outcomes 1) Crowd speed-congruency could have no influence; 2) Averaging of target and crowd speed might lead to faster responses on speed-congruent trials; 3) Within-colour contrast between target and crowd might lead to faster responses on speed-incongruent trials. Initial results support the third outcome, suggesting that task-irrelevant crowd speed is processed, but not averaged.