The Role of Vocal Complexity in Expressive Language Outcome: Developmental Course and Intervention Effects in Toddlers at Risk for ASD and Language Impairment
Up to 40% of later-born siblings of children with autism spectrum disorder (ASD) arediagnosed with: a) ASD (7-19%)1,2, which is defined by social communication impairments; or b) otherlanguage and/or cognitive delays (14-20%)3 by age three. The diverse language outcomes of these high-risk(HR) toddlers and the ability to observe them prior to overt symptom emergence make them an ideal samplefrom which to learn about sources of variability in language development and potential risk indicators oflanguage delays and disorders. Vocal complexity seems to be a strong predictor of later expressive languagein many populations, yet this construct has been understudied.4-13 For example, aspects of vocal complexityhave been found to predict later expressive language in typically developing (TD) and ASD children, but nostudies have examined this relation for HR toddlers. Also, previous studies of young children's earlyvocalizations have not distinguished between vocal complexity occurring within preverbal (non-word)vocalizations versus that occurring within words. Doing so may result in measures of vocal complexity that aresensitive to change across the second year of life. Low vocal complexity may signal early language difficultiesand need for intervention in HR toddlers.7-13 Further, vocal complexity may be malleable with intervention.Improving Parents as Communication Teachers (ImPACT) is a 12-week, naturalistic developmental behavioralintervention (NDBI) designed to improve social communication and language skills in toddlers with ASD.14-15ImPACT teaches parents to respond contingently to toddlers' vocalizations. Because parent responsiveness tochild vocalizations has been found to predict increased vocal complexity and better expressive language in TDand ASD children,16-18 it is plausible that ImPACT will also increase HR toddlers' vocal complexity. This project will examine vocal complexity within an ongoing NIDCD-funded longitudinal randomizedcontrolled trial (RCT) of ImPACT (compared to treatment as usual) in 12-27-month-old HR toddlers. Theproject will add a low risk (LR) sample and measures of vocal complexity and parent contingentresponsiveness. It will use longitudinal modeling and mediation analysis to examine 1) the growth of word vs.non-word vocal complexity and its relation to expressive language outcome in HR and LR toddlers;and 2) the role of the ImPACT intervention on a) parents' contingent responsiveness, b) toddlers'subsequent vocal complexity, and c) toddlers' expressive language outcome. This project will provideinsight into the role of vocal complexity as a risk indicator of ASD and language delay as well as its malleabilityin response to a parent-implemented social communication intervention. The proposed research and trainingplan will provide experience and mentorship to a talented and motivated young researcher, and it will be crucialfor the applicant's development as an independent and productive clinical scientist. �
Interagency Autism Coordinating Committee (IACC)
Autism Research Database (AFD)
