The Role of Prior Knowledge in Development of Visual-Auditory Integration

Recent research suggests that children do not combine multisensory information in an optimal manner until at least eight years (Nardini et al, Curr Biol. 2008; Gori et al, Curr Biol. 2008). Bayesian models propose that observers take into account the reliability of signals received, the prior probability of a given object or event, and the prior probability that two sensory events have the same cause (Kording et al, PLoS One, 2007). Children might not integrate multisensory cues if they lack prior knowledge about event pairings. We studied children's and adults' (1) propensity to bind different sounds with a visual event, and (2) their ability to learn new visual-auditory associations for interpreting events. Children aged 6, 8, and 10 years and adults judged whether moving balls appeared either to bounce or to pass without bouncing (Sekuler et al, Nature 1997). Collisions were accompanied by either beeps, white noise inclining in amplitude, white noise declining in amplitude, or silence. Each participant was re-tested after a training phase in which they saw unambiguous bounce events paired with one of these sounds. These initial results come from groups trained with the beep stimulus only. Before training, children were less influenced by a beep in their perception of the visual event than were adults, but the influence was stronger in 10 year olds than in younger children. Younger children were also less influenced by training with the new sound pairing than 10 year olds or adults. This study is the first to track performance in the “audiovisual bounce illusion” across this age range. We found an extended developmental trajectory for both the interpretation of visual events in light of auditory information, and the ability to learn new visual-auditory pairings. This is consistent with the hypothesis that prior knowledge is a factor limiting children's multisensory perception.