Development of Audiovisual Integration in Central and Peripheral Vision Yi-Chuan Chen, Terri L. Lewis, David I. Shore, and Daphne Maurer Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Canada Background Sound-induced flash illusion Fission1: Fusion2: For adults, fission is larger than fusion in periphery2,3 Inconsistent reports on developmental changes4,5,6 Results Accuracy of reporting number of flashes Inclusion criterion: accuracy in the centre/1F catch trials (children: 60%, adults: 80%) Age x Flash x Congruency interaction (p < .05) 1F no Age effect Congruent > Unimodal = Catch > Incongruent 2F Age effect in all conditions: Congruent: 7 < 20 (p < .005); Unimodal, Incongruent, and Catch: 7, 9 < 20 (ps < .01) Congruency effect at all ages: Congruent > Unimodal > Catch > Incongruent Magnitude of illusion (Accuracy of Congruent - Incongruent) Centre Age effect: fission and fusion both reduced with age, 7, 9 > 20 (p < .05) Periphery Age x Illusion (p < .05): Fission > Fusion in 11- and 20-year-olds (p < .005); but no difference in 7- and 9-year-olds. Signal detection theory: sensitivity (d’) and criterion (c) for flashes in the 1B and 2B conditions Sensitivity (d’) In both Centre and Periphery: increased with age (7, 9 < 20, p < .05) Periphery: fusion > fission only in 11 and 20 (p < .05) Criterion (c) Fission: No age effect Fusion: reduced with age (7, 9 > 20, p < .01) Flash Beep Perception +  c d’ 2 flashes 1 flash Response 2F 1F Stimulus (Flash) 1F 2F Response FA Hit Centre Periphery 1F Centre Periphery Goal To measure developmental changes in audiovisual integration in the centre and periphery using the sound-induced flash illusion * * 2F Participants 7-, 9-, 11-, and 20-year-olds (N = 20 in each age group) Stimuli Design: four factors Age: 7, 9, 11, 20 Location: Centre, Periphery (mean of left + right) Flash: 1F, 2F Congruency: Unimodal, Congruent, Incongruent, Catch 7 9 11 20 7 9 11 20 2⁰ 10⁰ Age (years) 7 9 11 20 7 9 11 20 Age (years) 17 ms Flash (F, white disc) Beep (B, white noise) SOA: 85 ms Catch trial SOA: 300 ms Time 10 ms Discussion Different developmental trajectories of fission and fusion in centre and periphery Centre: illusions reduced with age4 Periphery: pattern of larger fission than fusion revealed with age Mainly from changes in sensitivity Bayesian inference model for multisensory perception6 Perception inferred from prior assumption and sensory information One possible prior in the periphery: visual events more likely dynamic (fission > fusion) No such prior in the centre (fission = fusion) Different priors in centre and periphery may develop by age 11 Later than the age (age 8) to integrate audiovisual information in a statistically optimal fashion7 Centre Periphery * * 7 9 11 20 7 9 11 20 Unimodal Congruent Incongruent Catch (out of sync) 1F 0B 1B 2B (fission) 2B 2F 1B (fusion) Age (years) References 1 Shams, Kamitani, & Shimojo (2000). Nature, 408, 788. 2 Andersen, Tiippana, & Sams (2004). Cognitive Brain Res, 21, 301-308. 3 Wozny, Beierholm, & Shams (2008). J Vis 8(3): 24. 4 Nava & Pavani (2013). Child Dev, 84, 604-616. 5 Innes-Brown et al. (2011). Developmental Sci, 14, 1089-1099. 6 Tremblay et al. (2007). PLoS ONE 2(8): e742. 7 Gori, Sandini, & Burr (2012). Front Integr Neurosci, 6:77. This study is supported by James S. McDonnell Foundation and NSERC to DM Contact: chenyic@mcmaster.ca