Gibson (The ecological approach to visual perception, Houghton Mifflin, Boston, 1979/1986) defined affordances as opportunities for motor behaviors, and highly emphasized the interaction between perception and action. Research on children with developmental coordination disorder commonly reports difficulties in judgments of affordances (perception) and in postural control (action). However, how perception and action are coupled has not been studied yet. The present study sought to evaluate the relationship between control of postural sway and perception of affordances in children at risk for developmental coordination disorder (RDCD) and typically developing children (TDC). We hypothesized that the relationship between perception and action would differ between groups. Participants made a series of judgments about their maximum sitting height (SHmax) while standing with and without wearing 10 cm blocks on feet. Postural sway and the judgment accuracy were recorded. Our findings showed that RDCD swayed more during judgment sessions and made less accurate judgments compared to TDC. In addition, TDC reduced postural sway from inter-judgment to judgment sessions, whereas the postural sway of RDCD remained identical between sessions. Last, while TDC reduced postural sway across judgment trials and revealed a learning effect of the judgments about SHmax in the block condition, RDCD never modulated postural sway and did not learn their SHmax in both non-block and block conditions. Overall, modulation of postural sway differed between groups during judgment sessions and between inter-judgment and judgment sessions, whereby their perceptual judgments about SHmax were differentially influenced. To summarize, this study demonstrated a difference in perception and action coupling between RDCD and TDC.
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