This influential article, written by the originator of the applied behavior analysis (ABA) treatment approach to autism, describes how intensive behavioral intervention (40 or more hours per week) resulted in positive outcomes for about half of the children treated in his clinical study.

ABA treatment was given to 38 children with autism who were younger than four years of age. One group was known as the intensive group and received ABA therapy during most of their waking hours (40 or more hours per week), and included all significant people and environments in their everyday experience. The low-ABA group received ABA therapy 10 or fewer hours per week. A comparison of these two groups at the end of two years indicated that the children in the intensive group had significantly more school placements in higher grades as well as significantly higher IQs than those in the low-ABA group. In fact, the low-ABA group children were no different than children with autism who had not been treated with the ABA approach at all. The author points out that the effect on the intensive group was quite impressive for 9 out of the 19 children, resulting in normal-range IQ scores and allowing them to be placed into age-appropriate classes with their peers.