Strategies for reaching by individuals with mental retardation: empty and filled glasses

The purpose of this study was to assess the reaching strategies of individuals with mental retardation under different conditions. Much about reaching has been studied from the points of view of the optimization of the reading performance and the adaptation to the object's attributes. Few studies, however, have concerned reaching among individuals with mental retardation. Eight right-handed individuals with mental retardation reached for two types of glasses, one empty and the other filled with water. We translated the position of the index finger into X-Y-Z coordinate values and examined movement time, length of trajectory, and tangential velocity under the empty and filled conditions. There was no difference between conditions on any of the variables thought in many studies for individuals without mental retardation to indicate differences between attributes. This suggests that the present individuals with mental retardation might have difficulty in using information or context for planning movement and in optimizing their reaching movement for different conditions.