In his pioneering research, Dr. Ivar Lovaas used principles of Applied Behaviour Analysis to teach children a hierarchy of skills, all of which build upon each other to increase a child's behaviour in the areas of communication, language, observational learning, play, academics, general knowledge, social and independent living skills. His work revealed that by using this science, interventionists can in fact increase appropriate behaviours and decrease problem behaviours of children with autism, thereby improving their participation in daily life and educational settings.

Early intensive behavioural intervention for children with autism focuses on developing skills across a range of domains such as imitative skills, receptive and expressive language skills, academics, adaptive skills, social language, play skills and peer interaction skills. Teaching involves breaking complex skills down into small basic units of behaviour, guiding the child to demonstrate the behaviours, and providing positive reinforcement for doing so. Learning becomes a rewarding process, and ultimately, children with autism learn how to learn.

Children with autism characteristically do not learn readily from typical environments. At present, the only intervention for children with autism that is supported by credible scientific evidence is based upon the principles of Applied Behaviour Analysis. The delivery of such a programme can and should be comprehensive, in that it should use multiple methods to address a range of skill areas. It should also be intensive, in that one-to-one teaching should be provided at a high number of hours per week. Treatment should be provided as early as possible, and should occur at an intensive level for approximately two years. After this time, systematic support in an appropriate educational placement should take place, while supplemental home-based treatment should continue as appropriate to the child's needs.