This study investigated the notion that children with developmental coordination disorder (DCD) show a reduced capacity of internally simulating movements of their own body or motor imagery. Using a mental rotation paradigm the contribution of hand posture to laterality/mirror judgments of bodily and alphanumeric stimuli was studied in 13 children with DCD and 13 matched typically developing (TD) children. Children were asked to judge whether the stimulus on display, rotated over -90 degrees , -30 degrees , +30 degrees , or +90 degrees , was a right or left hand or a canonical or mirror-reversed letter. Analysis of accuracy (ACC) and response times (RTs) demonstrated that children with DCD were generally slower and made more errors. RTs to letter stimuli were faster than those to hand stimuli in both DCD and TD children. For both groups RTs profiles were influenced by the orientation of the stimulus, showing longer response times for larger rotations. Clockwise rotations of right hands resulted in slower judgments than did counterclockwise rotations, whereas the reverse was true for left hands. Moreover, the results also indicate a contribution of hand posture to the laterality judgments of hands, with longer RTs when the posture of the participants' hands was opposite to the posture of the hands on display. Importantly, these effects that suggest an imagery strategy engaging motor processes were present in both groups. Apparently, the children with DCD of the present study did rely on motor imagery to solve the mental rotation task; however, their judgments seem to be compromised by a less well-defined internal model.
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