Discourse Profiles in Autism Spectrum Disorder: A Family Study of Prosody

Background: Impairments in pragmatic (social) domains of language, including narrative and conversation, are a universal feature of autism spectrum disorder (ASD). Subtle differences in pragmatic language have been identified in a subset of parents of individuals with ASD with the broad autism phenotype (BAP; Landa et al., 1992), suggesting that familial characterization of pragmatic language may highlight genetic mechanisms underlying ASD. A crucial aspect of pragmatic language is prosody, or the intonation, stress, rate, and rhythm of speech, which is imperative for signaling communicative intent. Differences in prosody are a hallmark of the social-communicative profile of ASD, and subtler prosodic differences have been noted in first-degree relatives with the BAP (Landa et al., 1992; Losh et al., 2012).

Objectives:  To use automated, objective measures of prosody alongside clinical-behavioral measures in two separate contexts to characterize prosodic profiles in ASD and in parents.

Methods:  Males with ASD (n=47), their parents (n= 99), and respective control groups (n=22 male proband controls; n=46 parent controls) narrated the wordless picture book, Frog, Where Are You? (Mayer, 1969). Prosody was measured from recorded narrations using Praat (Boersma, 2001) to obtain mean fundamental frequency (f₀), standard deviation (SD) of f₀ and f₀ range (both measures of f₀ variability), f₀drop, and speaking rate. Pragmatic language was rated from semi-naturalistic conversation using the Pragmatic Rating Scale (PRS; Landa, 1992) and Pragmatic Rating Scale-School Age (PRS-SA; Landa, 2011). Acoustic variables of prosody during narration were examined in relation to pragmatic violations measured by the PRS and PRS-SA (using Principle Component Analysis) to explore how prosodic differences co-segregate with broader discourse profiles across contexts.

Results:  Males with ASD demonstrated significantly different utterance-final intonation patterns, consisting of f₀ decline compared to f₀ rise identified in controls (p<.01), marginally slower speaking rate (p=.08), and increased pauses (p=.08) during narration. When prosodic features were examined in the context of broader pragmatic abilities, reserved conversational styles in males with ASD (e.g., reduced reciprocity, poor response elaboration) were associated with greater SD, range of f₀, more pauses, and slower speaking rate (p<.07). The ASD parent group did not differ from controls in features of prosody during narration; however, similar to findings in ASD, a reserved conversational style was related to increased pauses and reduced speaking rate during narration (p<.07).

Conclusions:  Consistent with prior work, results indicate key areas of prosodic differences during narration in individuals with ASD and controls. Increased f₀ drop in the ASD group signals potential differences in control of the vocal mechanism to utilize varying intonation patterns, such as high-terminal rise, to highlight socially meaningful information (House, 2006). Though differences in f₀ variability were not identified between the ASD and control groups, prosodic features co-segregated with broader pragmatic styles, such that in the ASD group, those with a reserved discourse style demonstrated greater f₀ variability. Furthermore, reserved discourse styles were associated with increased pauses and reduced speaking rate in the ASD and ASD parent groups. Together, these results demonstrate that specific prosodic differences are closely related to differing broader discourse styles.