WWC review of this study

Randomized Trial of Intensive Early Intervention for Children with Pervasive Developmental Disorder.

Smith, Tristram; Groen, Annette D.; Wynn, Jacqueline W. (2000). American Journal on Mental Retardation, v105 n4 p269-85. Retrieved from: https://eric.ed.gov/?id=EJ617917

  • Randomized Controlled Trial
    , grade

Reviewed: August 2010

No statistically significant positive
Meets WWC standards with reservations
Cognition outcomes—Substantively important positive effect found for the domain
Comparison Period Sample Intervention
Significant? Improvement


Lovaas Model of Applied Behavior Analysis vs. Parent training


Full sample;
28 students





Evidence Tier rating based solely on this study. This intervention may achieve a higher tier when combined with the full body of evidence.

Characteristics of study sample as reported by study author.

  • Female: 18%
    Male: 82%

  • Urban
    • B
    • A
    • C
    • D
    • E
    • F
    • G
    • I
    • H
    • J
    • K
    • L
    • P
    • M
    • N
    • O
    • Q
    • R
    • S
    • V
    • U
    • T
    • W
    • X
    • Z
    • Y
    • a
    • h
    • i
    • b
    • d
    • e
    • f
    • c
    • g
    • j
    • k
    • l
    • m
    • n
    • o
    • p
    • q
    • r
    • s
    • t
    • u
    • x
    • w
    • y

  • Race
  • Ethnicity
    Not Hispanic or Latino    


Participants resided within a one-hour drive to the research site, located at the University of California–Los Angeles (UCLA) Young Autism Project.

Study sample

For this study, all referrals to the ULCA Young Autism Project were eligible if the following criteria were met: (1) referred to the treatment center between 1989 and 1992, (2) chronological age between 18 and 42 months, (3) residence within a one-hour drive of treatment center, (4) IQ ratio between 35 and 75, (5) diagnosis of autism or pervasive developmental disorder not otherwise specified, and (6) no other major medical problems. Of those determined to meet the criteria, one family declined, and eight others were determined not to be eligible. Children were divided into two strata: those with autism and those with other diagnoses. Within the strata, 32 children were divided into pairs based on IQ and randomly assigned to the treatment or comparison condition. After random assignment, four children with mental retardation and no pervasive developmental disorder were excluded. The final sample included 28 children (15 in the intervention group and 13 in the comparison group).

Intervention Group

The intervention for the treatment group was based on Lovaas’s behavior treatment model. The program was implemented with four to six student therapists, supervised by the study authors. Treatment occurred in the children’s homes for approximately 30 hours a week for two to three years. Participants’ primary caregivers were asked to conduct five hours per week of treatment alongside a student therapist for the first three months of treatment. In the beginning of the treatment, student therapists largely used one-to-one discrete trials, which involve a cue for behavior, guidance on the appropriate response, and reinforcement. As children mastered skills, the treatment progressed from simple tasks to more complex skills. Once the children entered school, student therapists served as aides to help the children adjust to classrooms, and the one-to-one treatment decreased as children progressed.

Comparison Group

Parents of children in the comparison group received training to use treatment approaches described in the Lovaas et al. (1981) manual. Parents received in-home training in two weekly sessions, totaling five hours per week, for three to nine months. The first author of the study met with parents at the first and last training sessions, and every three months in between. In the first session, parents were asked to identify three goals for the child, and the first author and parent trainer created a plan using the Lovaas approach to reach those goals. In subsequent sessions, the trainer would demonstrate the techniques, observe the parent, and provide feedback.

Outcome descriptions

Cognitive development was assessed with a measure of intellectual functioning, or IQ. For a more detailed description of this outcome measure, see Appendix A2.1.

Support for implementation

Training for student therapists for the intervention group was not explicitly stated. Trainers for the comparison group had a minimum of one year of experience at the UCLA Young Autism Project, which included at least six months instructing novice therapists. The trainers for the comparison group received one hour per week of individual supervision from the first author, with additional supervision as needed. The study authors had a combined experience of 10 years at the UCLA Young Autism Project under Lovaas’s supervision.


Your export should download shortly as a zip archive.

This download will include data files for study and findings review data and a data dictionary.

Connect With the WWC

back to top