Abstract
The present study examined age-related differences in multisensory integration and the effect of spatial disparity on the sound-induced flash illusion—-an illusion used in previous research to assess age-related differences in multisensory integration. Prior to participation in the study, both younger and older participants demonstrated their ability to detect 1–2 visual flashes and 1–2 auditory beep presented unimodally. After passing the pre-test, participants were then presented 1–2 flashes paired with 0–2 beeps that originated from one of five speakers positioned equidistantly 100cm from the participant. One speaker was positioned directly below the screen, two speakers were positioned 50cm to the left and right from the center of the screen, and two more speakers positioned to the left and right 100cm from the center of the screen. Participants were told to report the number of flashes presented and to ignore the beeps. Both age groups showed a significant effect of the beeps on the perceived number of flashes. However, neither younger nor older individuals showed any significant effect of spatial disparity on the sound-induced flash illusion. The presence of a congruent number of beeps increased accuracy for both older and younger individuals. Reaction time data was also analyzed. As expected, older individuals showed significantly longer reaction times when compared to younger individuals. In addition, both older and younger individuals showed a significant increase in reaction time for fusion trials, where two flashes and one beep are perceived as a single flash, as compared to congruent single flash trials. This increase in reaction time was not found for fission trials, where one flash and two beeps were perceived as two flashes. This suggests that processing may differ for the two forms for fission as compared to fusion illusions.
Highlights
Our senses were once believed to be modular and encapsulated, with information from one sensory modality being inaccessible to the other senses
Spatial disparity has been found to influence multisensory integration in a number of human and animal studies [21,22,23,24]. These studies found an effect of spatial disparity on multisensory integration and saccades [21], event related potentials [23], and neuronal activation of cells in superior colliculus [22] and auditory cortex [24]. Given this extensive literature demonstrating an effect of spatial disparity on multisensory integration, we examined the effect of spatial disparity on the sound induced flash illusion, and examined how this effect might vary with age
The present study examined the effect of spatial disparity on the sound induced flash illusion with spatial disparities larger than that used in previous research [20]
Summary
Our senses were once believed to be modular and encapsulated, with information from one sensory modality being inaccessible to the other senses. Any integration of information across the senses was thought to occur in specific “polysensory” areas of the brain [1,2]. Recent research has shown that this is incorrect with evidence that sensory processing is primarily multisensory in nature [3]. Spatial Disparity, and Multisensory Integration identified [4,5]. These findings suggest that unisensory processing that is isolated from other sensory modalities is uncommon. Given that sensory connections across multiple modalities have been found, research on how the senses interact is important in understanding the basic properties of sensory processing
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