What is Applied Behavior Analysis?
Applied Behavior Analysis (ABA) uses scientifically valid principles, such as positive reinforcement, to provide therapy that improves specific behaviors, such as verbal communication, and simultaneously evaluates whether changes in behvior are indeed the result of the therapy. ABA is self-evaluating and discovery-oriented because the uniqueness of children with disabilities requires a careful search for the most effective treatment, which will change over time. Parents, siblings, teachers and others should expect periods of observation and learning about the causes (antecedents) and effects (consequences) of problem behavior before therapies can be designed and applied. But you can also expect that when a therapy plan is applied there will be data showing its effectiveness.
The research supporting ABA is conclusive. The US National Library of Medicine provides a database of research articles, and a search for research on applied behavior analysis produces 400+ articles. There is also information on the websites of Autism Speaks and Wikipedia.