Applied Behavior Analysis (ABA) is perhaps the most popular approach in the treatment of autism and other pervasive developmental disorders. This teaching strategy has roots deep in the Behaviorist approach to psychology. It also serves to break complex tasks down into their most fundamental elements. The child is introduced to a task on its most fundamental level. Once the child masters the first step he is introduced to the next. The process is called chaining . One skill is linked to the next until the child has mastered the task. For example, if a therapist is using ABA to teach the student to color, he would begin with picking up the crayon. If the student follows through correctly, he is immediately rewarded. Once he demonstrates that he consistently follows through the next step would be introduced. Applied Behavior Analysis relies heavily on rewarding desired behavior and redirecting negative behavior. Negative behavior is typically ignored unless it is a non-negotiable like hitting. This approach is the foundation for drills and activities used in the treatment for autism such as discrete trial.