Contrast-marking prosodic emphasis in Williams syndrome: results of detailed phonetic analysis

Background: Past reports on the speech production of individuals with Williams syndrome (WS) suggest that their prosody is anomalous and may lead to challenges in spoken communication. While existing prosodic assessments confirm that individuals with WS fail to use prosodic emphasis to express contrast, those reports typically lack detailed phonetic analysis of speech data. The present study examines the acoustic properties of speech prosody, aiming for the future development of targeted speech interventions.

Aims: The study examines the three primary acoustic correlates of prosodic emphasis (duration, intensity, F0) and determines whether individuals with WS have difficulty in producing all or a particular set of the three prosodic cues.

Methods & procedures: Speech produced by 12 individuals with WS and 12 chronological age (CA)-matched typically developing individuals were recorded. A sequential picture-naming task elicited production of target phrases in three contexts: (1) no contrast: gorilla with a racket → rabbit with a balloon; (2) contrast on the animal: fox with a balloon → rabbit with a balloon; and (3) contrast on the object: rabbit with a ball → rabbit with a balloon. The three acoustic correlates of prosodic prominence (duration, intensity and F0) were compared across the three referential contexts.

Outcomes & results: The two groups exhibited striking similarities in their use of word duration and intensity for expressing contrast. Both groups showed the reduction and enhancement of final lengthening, and the enhancement and reduction of intensity difference for the animal contrast and for the object contrast conditions, respectively. The two groups differed in their use of F0: the CA group produced higher F0 for the animal than for the object regardless of the context, and this difference was enhanced when the animal noun was contrastive. In contrast, the WS group produced higher F0 for the object than for the animal when the object was contrastive.

Conclusions & implications: The present data contradict previous assessment results that report a lack of prosodic skills to mark contrast in individuals with WS. The methodological differences that may account for this variability are discussed. The present data suggest that individuals with WS produce appropriate prosodic cues to express contrast, although their use of pitch may be somewhat atypical. Additional data and future speech comprehension studies will determine whether pitch modulation can be targeted for speech intervention in individuals with WS.