Development of Restricted and Repetitive Behaviors from 15 to 77 Months: Stability of Two Distinct Subtypes?

A community sample of 192 parents reported on their children's restricted and repetitive behaviors (RRBs) at mean ages 15 months (N = 138), 26 months (N = 191), and 77 months (N = 125) using the Repetitive Behavior Questionnaire-2 (RBQ-2). Consistent with previous factor analytic research, 2 factors were found at each age: 1 comprising repetitive sensory and motor behaviors (RSM), and the other comprising insistence on sameness behaviors including rigidity, routines, and restricted interests (IS). Regression analyses indicated that RSM and IS subtypes develop independently. RSM at 77 months was predicted only by RSM behaviors at 26 months and not by IS behaviors at either 15 or 26 months nor by RSM behaviors at 15 months. IS at 77 months was predicted by IS behaviors at both 15 and 26 months, but not by RSM behaviors at either 15 or 26 months. Our findings provide evidence that there is stability of 2 independent subtypes of RRBs, RSM and IS, across early childhood and that these subtypes develop independently of each other.