Multisensory uncertainty reduction for hand localization in children and adults.

Adults can integrate multiple sensory estimates to reduce their uncertainty in perceptual and motor tasks. In recent studies, children did not show this ability until after 8 years. Here we investigated development of the ability to integrate vision with proprioception to localize the hand. We tested 109 4- to 12-year-olds and adults on a simple pointing task. Participants used an unseen hand beneath a table to point to targets presented on top of the table to vision alone, proprioception alone, or both together. Overall, 7- to 9-year-olds' and adults' points were significantly less variable given vision and proprioception together compared with either alone. However, this variance reduction was present at all ages in the subset of participants whose proprioceptive estimates were less than two times more variable than their visual. These results, together with analyses of cue weighting, indicate that all groups integrated vision and proprioception, but only 7- to 9-year-olds and adults consistently selected cue weights that were appropriate to their own single-cue reliabilities. Cue weights used at 4-6 and 10-12 years still allowed over half of participants at these ages to reduce their pointing variability. One explanation for poorer group-level cue weighting at 10-12 years is that this ages represents a period of relatively rapid physical growth. An existing Bayesian model of hand localization did not describe either adults' or children's data well, but the results suggest future improvements to the model.