Treatment Intensity Predicts Target Mastery and Developmental Change in Early Intensive Behavioral Intervention

PURPOSE: To examine whether prospectively recorded, delivered one-to-one treatment intensity predicted learning and developmental outcomes in children receiving Early Intensive Behavioral Intervention (EIBI). METHODS: Thirty-nine autistic children receiving EIBI were followed for 18 months. Delivered treatment hours and mastered treatment targets were recorded weekly. Between-child analyses tested whether each child's average weekly intensity predicted average targets mastered per week and 12-month change in the Learning Accomplishment Profile-Third Edition (LAP-3) developmental index. Descriptive child-week analyses examined associations between weekly intensity and target mastery. RESULTS: Average intensity predicted average targets mastered per week, accounting for 45.5% of the variance (N = 39, p < .001), and remained predictive after adjustment for baseline chronological age and developmental index. Across 1,970 positive-hour child-weeks, greater weekly intensity was descriptively associated with more mastered targets. Average intensity and average target mastery also predicted 12-month change in LAP-3 developmental index. CONCLUSION: Higher delivered one-to-one intensity was associated with faster target mastery and greater developmental-index change. Because intensity was not experimentally assigned and weekly observations were nested within children, the findings support prediction rather than causal inference or a universal optimal dose.