Abstract
We measured developmental changes (7-, 9-, and 11-year-olds, and adults) in audiovisual integration utilizing the visual fission and fusion illusions induced by sounds. In the fission illusion, a single flash is perceived as two flashes when accompanied by two beeps. In the fusion illusion, two flashes are perceived as a single flash when accompanied by a single beep. The flashes were presented in the centre or 10° in the periphery. The results revealed different developmental changes for the fission and fusion illusions in the centre and periphery. In the centre, fission and fusion decreased with age (p <.05, post-hoc tests revealed that the magnitude was smaller in adults than 7- and 9-year-olds, ps <.05), and there was no difference in the pattern for the two illusions (no main effect and no interaction, ps > .33). In contrast, in the periphery, fission was larger than fusion (p <.001), and this difference increased with age (p <.05, post-hoc tests revealed that the difference was larger in adults than 7- and 9-year-olds, ps <.05); however, there was only a marginal effect of age on magnitude of the illusions (p = .06). A further analysis based on signal detection theory demonstrated that these developmental changes in central and peripheral vision were partly caused by changes in sensitivity (d') to the flashes. These results suggest that developmental trajectories of audiovisual integration in the centre and periphery are different, and that, with age, peripheral vision becomes more susceptible than central vision to different types of audiovisual integration (i.e., fission vs. fusion). The results also demonstrate that audiovisual integration in central and peripheral vision does not become adult-like until 11 years of age, at least as measured by these two illusions.
Meeting abstract presented at VSS 2014