Bayesian causal inference in visuotactile integration in children and adults.

If cues from different sensory modalities share the same cause, their information can be integrated to improve perceptual precision. While it is well established that adults exploit sensory redundancy by integrating cues in a Bayes optimal fashion, whether children under 8 years of age combine sensory information in a similar fashion is still under debate. If children differ from adults in the way they infer causality between cues, this may explain mixed findings on the development of cue integration in earlier studies. Here we investigated the role of causal inference in the development of cue integration, by means of a visuotactile localization task. Young children (6-8 years), older children (9.5-12.5 years) and adults had to localize a tactile stimulus, which was presented to the forearm simultaneously with a visual stimulus at either the same or a different location. In all age groups, responses were systematically biased toward the position of the visual stimulus, but relatively more so when the distance between the visual and tactile stimulus was small rather than large. This pattern of results was better captured by a Bayesian causal inference model than by alternative models of forced fusion or full segregation of the two stimuli. Our results suggest that already from a young age the brain implicitly infers the probability that a tactile and a visual cue share the same cause and uses this probability as a weighting factor in visuotactile localization.