Using a lag reinforcement schedule to increase phonemic variability in children with autism spectrum disorders.

Shaping functional vocal language is difficult when an individual has not yet acquired an echoic repertoire and does not emit sufficient phonemes (i.e., speech sounds) for shaping. Few studies have evaluated interventions to increase the frequency and breadth of phonemes. The current study extended Esch, Esch, and Love (2009) by evaluating the effects of a Lag 1 reinforcement schedule on vocal variability and limiting the definition of variability to responses that incorporated a novel phoneme. For 2 of the 3 participants, the cumulative number of novel phonemes, the percentage of trials with variability, and the number of different phonemes emitted per session increased during the Lag 1 intervention phase.