Detection of Syllable Stress in Autism Spectrum Conditions

Background: Prosody plays an important role in a range of communicative functions that have been categorized as affective, pragmatic and grammatical (Roach, 2000). Previous studies on prosody perception in autism spectrum conditions (ASC) using complex speech paradigms have reported strong evidence for impairments in the processing of affective and pragmatic/interactional cues (see review O’Connor, 2012). A possible explanation for these difficulties may stem from lower level ability in acoustic perception of linguistic information in ASC. In particular, the perception of word stress has been shown to play a crucial role for language acquisition and phonological awareness (e.g., Kaye, 1988).

Objectives: This study aimed to explore the possibility that the prosodic deficits observed in ASC may be stem from difficulties in the detection of prominent patterns of syllables within a word by using a simple speech paradigm to assess acoustic detection of syllable stress in adults with and without ASC.

Methods: A same-different stress perception task (Leong et al., 2010) was administered to a sample of 21 adults with high-functioning ASC and 21 IQ and age matched controls to assess discrimination ability of syllable stress differences between pairs of identical 4-syllable words (i.e. DEmocracy – deMOcracy). Also, the Communication Checklist-Self Report (Bishop, Whitehouse & Sharp, 2009) was used to assess three domains of communicative skills (language structure, pragmatics, social engagement).  The protocol for the study received ethical approval from the University of Portsmouth Ethics Committee which follows the guidelines of the British Psychological Society.

Results: The results showed that the ASC group found it significantly more difficult than the comparison sample to judge stress between pairs of identical words. Also, correlational analyses demonstrated an association between syllable stress perception and pragmatic skills in ASC.

Conclusions: To our knowledge this is the first evidence for syllable stress perception deficits in ASC and for a link between syllable stress perception and pragmatic skills. Our findings that high-functioning adults with ASC show impairments in speech processing, suggest the possibility of more severe deficits in low-functioning ASC. Intact detection of intonational and rhythm patterns of speech is crucial for linguistic, cognitive, emotional and social development (e.g. Murray, 1992; Matychuk, 2005). A better understanding of the difficulties people with ASC have with interpreting syllable stress could potentially help us understand why these individuals display impairments in the processing of linguistic, affective and pragmatic information.