Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Joseph R. Scotti

Committee Co-Chair

Kennon A. Lattal

Committee Member

Cheryl McNeil

Committee Member

Tracy Morris

Committee Member

Susannah Poe


Autism spectrum disorders (ASDs) are disorders characterized by repetitive and stereotyped behavior. Research shows that these behaviors interfere with typical development and with the acquisition of new skills, including vocal communication. For many children with ASD who are unable to imitate others and who have limited vocal repertoires, few vocal training interventions are available. Research on operant variability, however, indicates that the direct reinforcement of varied sounds may create a larger set of vocal responses. This enlarged response class could then be used to shape functional vocal communication. In the first of three studies, the existing vocal repertoires of 10 children with ASD were assessed for level of variability within vocalizations and for phoneme production. Three children with moderate to low vocal variability then were exposed to lag schedules of reinforcement. All participants produced new phonemes under these conditions, but novel vocalizations increased for only one. The final study investigated whether this increased variability could be maintained when exposed to reinforcement delivered independent of variability (i.e., yoked control). Limitations and suggestions for future research are discussed.