Postcoincidence trajectory duration affects motion event perception

In a two-dimensional display, identical visual targets moving toward and ac ross each other with equal, constant speed can be perceived either to rever se their motion directions at the coincidence point (bouncing percept) or t o stream through one another (streaming percept). Although there is a stron g tendency to perceive the streaming percept, various factors have been rep orted to induce the bouncing percept, such as a sound or a visual flash at the moment of the visual target coincidence. By changing duration of the po stcoincidence trajectory (PCT), we investigated how long it would take for such bounce-inducing factors to be maximally effective after the visual coi ncidence. With bounce-inducing factors, the percentage of the bouncing perc ept did not reach its maximal level immediately after the coincidence but i ncreased as a function of PCT duration up to 150-200 msec. The results clea rly reject the possibility of the cognitive-bias hypothesis about the bounc e-inducing effect and suggest rather that the bounce-inducing factors have to interact with the PCT for some period after the coincidence to be maxima lly effective.