A systematic literature search for studies reporting effects of Early Intensive Behavioral Intervention identified 34 studies, 9 of which were controlled designs having either a comparison or a control group. We completed a meta-analysis yielding a standardized mean difference effect size for two available outcome measures: change in full-scale intelligence and/or adaptive behavior composite. Effect sizes were computed using Hedges's g. The average effect size was 1.10 for change in full-scale intelligence (95% confidence interval = .87, 1.34) and .66 (95% confidence interval = .41, .90) for change in adaptive behavior composite. These effect sizes are generally considered to be large and moderate, respectively. Our results support the clinical implication that at present, and in the absence of other interventions with established efficacy, Early Intensive Behavioral Intervention should be an intervention of choice for children with autism.

We evaluated outcomes for 31 children with autism (2–6 years of age at intake) who received behavioral intervention in mainstream pre-school settings and a comparison group of 12 children receiving treatment as usual. After 2 years, children receiving behavioral intervention had higher IQ scores (Hedges g = 1.03 (95% CI = .34, 1.72) and adaptive behavior composite scores (Hedges g = .73 (95% CI = .05, 1.36). Despite probably fewer intervention hours, these group level outcomes were comparable to studies providing more intensive intervention. Individual child data also showed positive results with 19.4% achieving change at a reliable level for IQ; but a lower percentage than found in recent meta-analysis research. Strengths and weaknesses of the mainstream pre-school delivery model are discussed.

Following pretraining with everyday objects, 10 children aged from 1 to 4 years were given common vocal tact training with a set of three pairs of arbitrary stimuli of differing shapes; Set 1. Nine children learned to tact one stimulus as "zog" and the other as "vek" in each pair, and all passed subsequent pairwise tests for the corresponding listener behavior to each listener stimulus (i.e., /zog/ and /vek/, respectively). The children were next trained to clap to one stimulus of Pair 1 and wave to the other, and all then showed name-consistent transfer of these behaviors to the stimuli of Pair 2 and Pair 3. Seven children also were given a test of listener responding to experimenter-modeled clap and wave gestures, respectively, which they all passed. Four of the children next participated in a category match-to-sample test for the Set 1 stimuli; all 4 passed. For each pair of two additional six-stimuli sets, Set 2 and Set 3, 3 children were trained to wave to one stimulus and to clap to the other. For each set, all 3 children showed perfect transfer of the vocal tacts trained to Set 1, and of listener behavior both to the auditory stimuli /zog/ and /vek/ and to experimenter-modeled clap and wave gestures. They also sorted the stimuli perfectly in category match-to-sample tests for Set 2, Sets 1 and 2 combined, Set 3, and Sets 1, 2, and 3 combined. The results show that even in very young children, naming is a powerful means of generating new category relations among as many as 18 arbitrary stimuli.

We gathered individual participant data from 16 group design studies on behavioral intervention for children with autism. In these studies, 309 children received behavioral intervention, 39 received comparison interventions, and 105 were in a control group. More children who underwent behavioral intervention achieved reliable change in IQ (29.8%) compared with 2.6% and 8.7% for comparison and control groups, respectively, and reliable change in adaptive behavior was achieved for 20.6% versus 5.7% and 5.1%, respectively. These results equated to a number needed to treat of 5 for IQ and 7 for adaptive behavior and absolute risk reduction of 23% and 16%, respectively. Within the behavioral intervention sample, IQ and adaptive behavior at intake predicted gains in adaptive behavior. Intensity of intervention predicted gains in both IQ and adaptive behavior.

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