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Marko Nardini, Rachael Bedford, Meera Desai, Denis Mareschal; Fusion of disparity and texture cues to slant is not mandatory in children. Journal of Vision 2010;10(7):494. doi: 10.1167/10.7.494.
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© ARVO (1962-2015); The Authors (2016-present)
Integrating sensory cues can lead to “fused” percepts in which the ability to judge the component cues is lost. In recent studies, children did not integrate cues across modalities until 8 years or later. One hypothesis for this late development is that keeping cues separate and avoiding fusion is adaptive in allowing senses to be calibrated against each other while the body is growing. To test whether children do keep cues separate, we studied development of integration and fusion within the single modality of vision. We measured discrimination (d′) in 6-year-olds (n=20) and adults (n=20) for whether two discs were of same or different slant, given single or combined interocular disparity and texture cues. Observers judged slant differences of 12.5° (adults) or 25° (children), which made single-cue stimuli equally discriminable for the two groups. In combined-cue conditions, differences in discs' slants were either in the same direction in terms of both disparity and texture, or in opposite directions. “Integration” predicts better slant discrimination given two cues in the same direction than either cue alone. “Fusion” predicts worse discrimination given two cues in opposite directions than either cue alone. Adults showed significantly better slant discrimination (d′) given two consistent cues (“integration”) and significantly worse discrimination given two inconsistent cues (“fusion”). Six year olds showed neither effect, but had combined-cue discriminations intermediate to those for single cues, consistent with following one or other cue on each trial. Thus, while combining cues confers an advantage on adults when the cues agree, not combining cues confers an advantage on 6-year-olds when the cues disagree. Six-year-olds' ability to keep disparity and texture information separate enables them to detect a type of cue conflict that adults cannot. Such conflicts may provide the error signals needed for sensory recalibration as interocular distance changes in childhood.
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