Vocal Prosody in Autism: Understanding the Effects of Enhancing Vocal Prosody on Children's Comprehension and Retention of Story Narratives

Background: Therapists working with children with Autism Spectrum Disorders (ASD) frequently adjust the way they speak to what helps the individual child, often manipulating their vocal prosody and expressivity to better engage the child and help him focus as well as to process information better. Typically, therapists are unaware that they are doing so. Research to date on intervention outcomes with ASD children has never focused on the benefits of enhancing expressivity, whether in voice, face, or gestures. In fact, very few intervention approaches use highlighting of affect or expressivity as a specific strategy for ASD. (Greenspan & Wieder's DIR/Floortime and Gutstein's RDI do, but for these approaches, there is a paucity of outcome research.) It may well be, however, that enhancing prosody may be a key strategy to help children with ASD. Objectives: The purpose of the study was to measure the effects of prosodic style, specifically enhancement of vocal prosody, on narrative recall performance in children with ASD vs. Typical Development (TD). Results on a small number of participants were reported at IMFAR, 2008. The present study is a continuation of the previous one, with more subjects having now been seen. Methods: Seventy-nine participants (ages 4-8) underwent diagnostic and neurocognitive assessment. Thirty-seven children were classified into the ASD group; forty-two into the TD group. Two stories were developed about interpersonally dynamic and affectively-charged events, rich in factual and social cognitive information. They were produced in three prosodic modes. (E) Enhanced, (S) Standard, (D) Disconnected. In E, prosody highlighted story content and meaning at multiple levels (using affective, pragmatic, and grammatical prosody). S used typical prosody. In D, words were recorded randomly, concatenated into sentences, and acoustically modified to have continuous pitch and energy contours. Additional signal modification methods were used to match all modes on average pitch, energy, speaking rate, and pause duration. Separate questions were developed for factual and social-cognitive aspects of the story. Results: ANOVA analysis, with Prosodic Mode (E vs. S vs. D), Group (ASD vs. TD), and Story as independent variables, resulted in a significant interaction between Group and Prosodic Mode, with ASD children significantly better able to answer narrative questions as prosody intensity increased from D to S to E; no such beneficial effect of prosodic mode was seen for TD. Trends were found for this interaction to be more pronounced for the social cognitive questions. TD performed better than ASD in all prosodic modes; but in E compared to D, the TD-ASD difference was significantly reduced. Conclusions: These results extend and confirm the findings from a smaller group of ASD and TD children reported in 2008. They suggest that enhanced prosody specifically targeted to highlight the multiple levels of information in complex verbal communication helps comprehension and retention of information in children with ASD, in particular, social cognitive information. This has important implications for intervention as well as for assessment.