View article

Grip selection tasks have been used to test “planning” in both autism and developmental coordination disorder (DCD). We differentiate between motor and executive planning and present a modified motor planning task. Participants grasped a cylinder in 1 of 2 orientations before turning it clockwise or anticlockwise. The rotation resulted in a comfortable final posture at the cost of a harder initial reaching action on 50% of trials. We hypothesized that grip selection would be dominated by motoric developmental status. Adults were always biased towards a comfortable end-state with their dominant hand, but occasionally ended uncomfortably with their nondominant hand. Most 9-to 14-year-olds with and without autism also showed this “end-state comfort” bias but only 50% of 5-to 8-year-olds. In contrast, children with DCD were biased towards selecting the simplest initial movement. Our results are best understood in …