Abstract
This study investigated audiovisual integration in visual motion perception among both younger and older adults. Participants were asked to discriminate the visual motion direction of a random dot kinematogram in two experiments. The visual motion coherence of the random dot kinematogram varied across trials. Two experimental conditions were established: the lateral-shift and the one-sided sound condition. In the lateral-shift sound condition, the auditory motion stimulus based on interaural level differences was presented simultaneously with the visual stimuli. The auditory stimulus moved horizontally in either a rightward or leftward direction. In the one-sided sound condition, an auditory stimulus was presented through only one side of the headphones, simultaneously with the visual stimuli. The velocity of the dot motion differed between the two experiments (Experiment 1: 8°/s; Experiment 2: 6°/s). The results showed that the point of subjective stationarity was biased in the opposite direction to the auditory motion in the lateral-shift sound condition compared to the one-sided sound condition, regardless of age. Only in the Experiment 2, the point of subjective stationarity in the lateral-shift sound condition was more biased in older adults than in younger adults. These findings suggest that, in slow visual motion, age-related differences influence audiovisual motion integration.