During training sessions, IOA on attending, imitation of vocal scripts, and imitation of actions was calculated as the number of intervals or trials with agreements divided by the number of agreements plus disagreements multiplied by 100. During probe sessions and generalization sessions, IOA on scripted verbalizations, unscripted verbalizations, scripted play actions, and unscripted play actions, was calculated as dividing the smaller frequency of each response by the larger frequency of each response and multiplying by 100.