Effects of a contingent responses intervention on the quantity and quality of vocalizations of preschool children with autism spectrum disorder

Multiple contemporary theories emphasize the quantity and quality of child vocalizations for promoting spoken language acquisition. Yet, empirical evidence for facilitating vocal development is strikingly lacking including for children with autism spectrum disorder (ASD) who have difficulty developing language. We evaluate use of contingent responses and vocal enhancement strategies to increase the quantity and quality of child vocalizations to which adults can respond with language-facilitating input for children with ASD. Three preschool children with ASD and minimal verbal skills participated. Using an alternating treatments design embedded within a multiple probe across participants design, we compared using contingent responses with and without vocal enhancement strategies versus a non-contingent control condition. Based on visual analysis and effect sizes, all participants showed a functional relation between both active intervention conditions and quantity of vocalizations, as predicted. For quality of vocalizations, changes under the active intervention conditions were less pronounced than those observed for quantity. Two participants showed a functional relation between at least one quality variable and the active interventions. Our hypothesis that vocal enhancement strategies would exhibit a value-added effect was partially supported for quantity and quality. Findings support using contingent responses to improve the quantity and to some degree the quality of vocalizations in young children with ASD and minimal verbal skills. Support for the added value of vocal enhancement strategies was mixed. Refining the intervention strategies is warranted to meet the needs of the understudied population of children with ASD and minimal verbal skills.