Unstable or Stable? Prosodic Features and Voice Quality in Autism Spectrum Disorder: A Systematic Review and...

Speech prosody is fundamental to human spoken communication, and it is frequently characterized by atypical patterns, alongside voice quality, in individuals with autism spectrum disorder (ASD). However, findings across studies regarding these acoustic features in ASD remain inconsistent.

Literature searches across four databases identified eligible studies comparing prosodic or voice quality acoustic parameters between individuals with ASD and matched TD individuals. A total of 40 studies involving 1023 individuals with ASD and 929 TD individuals were included. Subgroup and meta-regression analyses were conducted to assess potential moderators.

The meta-analyses revealed a significantly higher mean pitch (Hedges' g = 0.43), broader pitch range (g = 0.29), and higher pitch standard deviation (g = 0.22) in the ASD group. For voice quality, significantly reduced shimmer (g = -0.44) and a trend toward reduced jitter (g = -0.26) indicated heightened stability of vocal fold vibrations in ASD.

Our findings reveal a seemingly paradoxical acoustic profile in ASD: while individuals with ASD exhibit suprasegmental instability, they also demonstrate voicing hyper-stability. Moderators identified after subgroup and meta-regression analyses, including language background, IQ status, age span, mean age, and task type, may further moderate the prosodic features.