First, assignment to groups was based on whether or not therapists
were available to provide intensive treatment rather than on a more
arbitrary procedure, such as the use of a random numbers table. Thus,
assignment could have been biased
Third, selection criteria such as IQ cut-offs
may have been unduly restrictive, yielding a sample with an unusually
favorable prognosis
Fourth, the large amount of treatment and the
level of expertise required for proper implementation may have been
too much for other professionals to duplicate, too stressful for most
children and families to tolerate, and too costly for funding agencies to support
Children in these studies received fewer hours of treatment
(18 to 25 hours per week vs. 40 hours) from less experienced
personnel than in the Lovaas study
All studies showed substantial
average increases in nonverbal IQ (22 to 29 points), but gains in other
areas were smaller than those reported by Lovaas (1987).
we conducted a fully randomized clinical trial with uniform, comprehensive
assessment protocols for all participants