Aging, Spatial Disparity, and the Sound-Induced Flash Illusion

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.

Multisensory integration in hemianopia and unilateral spatial neglect: Evidence from the sound induced flash illusion

“…At the behavioral level, in healthy participants, the fusion illusion seems overall less reliable and weaker than the fission illusion, and also more vulnerable to inter-individual variability (Shams et al, 2000;Andersen et al, 2004Andersen et al, , 2005Mishra et al, 2008;Innes-Brown and Crewther, 2009); we also did not find evidence for a correlation between the two illusions in both healthy (old and young) individuals and in brain-damaged patients. Moreover, aging seems to differently influence the perception of 'fission' and 'fusion' illusions: a larger susceptibility to fission effects, as 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 21 compared with fusion effects, was recently described in older participant (over 65 years, and of an average age comparable to that of our healthy participants), as compared with younger (18-30 years) adults (McGovern et al, 2014;DeLoss and Andersen 2015). Our control experiment in healthy participants confirms that the fission illusion is overall similar in younger (< 30 years) and older adults (> 50 years), while the fusion illusion seems to be lost in the elderly.…”

Effects of Repetition Suppression on Sound Induced Flash Illusion With Aging

“…One study showed that old adults demonstrated a significantly greater reaction time (RT) benefit when processing concurrent VS coactivation, while young adults demonstrated a significant increase in the magnitude of AV and AS coactivation (Mahoney et al, 2011). Therefore, there is debate about the evidence for audiovisual integration in old adults (DeLoss et al, 2013;McGovern et al, 2014;DeLoss and Andersen, 2015;Chan et al, 2018).…”

The Magnitude of the Sound-Induced Flash Illusion Does Not Increase Monotonically as a Function of Visual Stimulus Eccentricity

“…While manipulating the temporal proximity of audiovisual stimuli has a systematic effect on SIFI susceptibility, the impact of spatial manipulations of the stimuli are less clear. For instance, two studies found no impact of spatial disparity between auditory and visual stimuli on susceptibility to either the fission or fusion form of the SIFI (Innes-Brown & Crewther, 2009;DeLoss & Andersen, 2015). On the other hand, three studies provided evidence for greater fission susceptibility when the visual stimulus occurred in the periphery of the visual field compared to the fovea at 5 degrees (Tremblay et al, 2007), 8 degrees (Shams, et al, 2001) and 10 degrees (Chen, et al, 2017) eccentricity.…”