Associations Between Fundamental Frequency and ASD Symptoms in Preschoolers: Stability and Change Over Time

A hallmark of autism spectrum disorder (ASD) is atypical prosody, including differences in rhythm, stress, and intonation (fundamental frequency; F₀). Although prior work suggests F₀ differences between ASD and typically developing (TD) individuals, evidence in preschoolers remains limited and inconsistent, despite this being a critical period for prosodic development and the most common age at which children receive an ASD diagnosis. This study examined objectively measured F₀ features in preschool-aged children in ASD, developmental delay (DD), and TD groups to assess stability and change over time, group differences, and associations with ASD symptoms.

Children's vocalizations were recorded using child-worn SONY recorders during a naturalistic, play-based assessment (Brief Observation of Social Communication Change; BOSCC) administered up to 6 sessions per child (M=4.4, SD=1.3). ASD symptoms (Social Communication (SC), Restricted and Repetitive Behaviors (RRBs), and Total) were coded from BOSCC sessions. Whisper-large models were used for speaker diarization and audio spectrogram transformer models were used for speech classification and F₀ feature extraction.

Greater mean F₀ was associated with lower total ASD and SC scores, indicating fewer overall ASD symptoms and less social communication difficulties. Associations with F₀ variability differed by language level: among children with fluent speech, greater variability in mean F₀ was linked to greater total ASD and SC symptoms, while no associations were observed in minimally verbal children. No associations were found between F₀ features and RRB scores. F₀ features showed moderate stability across sessions with no longitudinal change and group differences in F₀ Range (TD and DD>ASD) and SD of mean F₀ (ASD>TD). 

Overall, findings suggest that intonation-related features, particularly mean and variability of F₀, show associations with total ASD symptoms and social communication in early childhood, underscoring the importance of continued research using longitudinal, naturalistic speech samples.