Proximal versus distal control in proprioceptively guided movements of motor-impaired children

Two groups of 7-year-old children diagnosed as motor-impaired (N = 6) or as controls (N = 6) were required to perform a task that involved locating targets under a table-top with one hand while attempting to match the position of the target with the other, on the table-top (intra-modal matching), always without visual control. The experimental design involved three different conditions: proximal control (P), distal control (D) or both (PD). Target distance errors were analysed in terms of absolute (AE) and variable error. When the scores for each hand were combined, the motor- impaired group showed inferior mean performance (AE scores) on all three conditions as compared with the control children and were also more variable in their behaviour. Analyses of scores achieved with the right and the left hand separately, however, demonstrated that the difference could largely be attributed to the scores obtained when matching with the right hand in conditions P and PD, and matching with the left hand in condition D. Possible explanations of these findings are discussed in the context of 'delay' (developmental lag) and/or 'deviancy' (neurological lesion/disconnection).