The experimental (research) portion of the treatment is to assess the effects of risperidone (Risperdal) on learning performance and motor movements in children. This study is looking at whether or not risperidone improves performance on certain cognitive-motor tasks. It is also looking to detect any negative side effects that the medicine has on children's body movements. Risperidone is often used to treat children with disruptive behaviors. This study will involve 18-20 children who are being treated by their own physicians with risperidone (for duration of 4 months or longer) for such behavior problems.