UC Riverside

Recent research has demonstrated that multisensory integration, once thought to be isolated to later stages of processing in polysensory areas, may play a significant part in nearly all sensory processing. A large volume of research has also found a wide array of perceptual and cognitive changes with age. Given these sensory declines, we would also expect similar declines in multisensory integration. The present studies examined age-related changes in multisensory integration using the sound-induced flash illusion. The illusion is studied by presenting a number of visual flashes paired with a discrepant number of auditory beeps. The first experiment examined multisensory integration in younger and older individuals using the sound-induced flash illusion. Older individuals were found to have stronger multisensory integration as compared to younger individuals. The second experiment examined whether this increased integration could be due to decreased inhibitory control in older individuals, or a decrease in their ability to ignore the auditory beeps. This was examined by including an unrelated task in the visual and auditory modalities. The results of the study found that the addition of the task did influence the strength of the illusion in both older and younger individuals. However, this did not differ by age, indicating that attentional differences are not the cause of increased integration in older individuals. The third experiment examined whether the strength of the visual and auditory stimuli influences the strength of integration and whether this differs for older and younger individuals. The strength of the stimuli was found to influence the strength of the illusion, with decreased stimulus strength increasing the strength of the illusion. No age-related differences were found for the sound-induced flash illusion. However, older individuals showed a greater change in integration with decreased stimulus strength for the reverse illusion in which participants report the number of beeps presented instead of the number of flashes. Lastly, the fourth experiment examined whether spatial disparity influences the illusion and whether this changes with age. Spatial disparity between the auditory and visual flashes was not found to influence the illusion to a high degree and no age-related differences were found.