Auditory Temporal Perception Is Enhanced in Children with ASD

Background: Pitch and time are two fundamental dimensions of auditory perception. In Autism Spectrum Disorders (ASD), enhanced pitch perception has been reported (Bonnel, 2010), providing support for an auditory basis for the enhanced perceptual functioning (EPF) model of ASD (Mottron, 2006). However, the temporal resolution of auditory perception in ASD has been less studied. Here, we developed a task that allows testing the accuracy of both pitch and time judgments using analogous stimuli within the same participants.

Objectives:  The aim of this study was to compare accuracy of fine-grained auditory pitch and time judgments between children with ASD and typically developing (TD) controls.

Methods:  Participants were 36 ASD and 27 TD children from the NeuroDevNet project (Zwaigenbaum et al, 2011). Groups were age-matched (mean 12.5 years, range 7-17) and had IQ>70. ASD participants were diagnosed using ADI-R and ADOS. In the Pitch-Time task, reference stimuli consisted of 5 harmonically complex tones (3 harmonics) at 500 Hz, each 100 ms in duration, with an onset-to-onset interval of 350 ms. Participants judged whether the 5 tones were the “same” (reference stimuli) or “different” (pitch or time manipulation). In the Pitch condition, half of the trials had the 4th tone changed in pitch by up to 300 cents. In the Time condition, half of the trials had the 4th tone shifted in time by up to 200 ms. Pitch and Time conditions were presented in separate counterbalanced blocks. Accuracy (percent correct) on the task was calculated by splitting the “different” levels into 4 bins of interest having center values of 3.1, 9.4, 18.8 and 37.5 cents (Pitch), and 14, 35, 49 and 63 ms (Time). Effects of group and level on accuracy were assessed for each condition via ANOVA, and per-level comparisons were made using Student’s t-test with Bonferroni correction across the 4 bins (p < .0125).

Results:  Participants with ASD were more accurate overall compared to the TD group on the Time condition (F(1,38.9)=5.7, p=.02; Figure 1). Accuracy varied across time levels in both groups (F(3,106.5)=91.7, p<.001). The greatest group difference was at the 35 ms Time level (t(23.7)=3.1, p=.006, 95% confidence interval 3.9%-20.2%). In the Pitch condition, accuracy varied significantly across pitch levels (F(3,142.5)=132.4, p<.001), but there was no group difference on the overall score or for any pitch level (all p>.15; Figure 2).

Conclusions:  The results provide new evidence for enhanced auditory perception in the time domain in ASD. Accuracy of temporal judgments was greater overall in the ASD group, and this effect was most pronounced for judgments of time manipulations around 35 ms. This enhancement is consistent with and extends our understanding of low-level perceptual advantages under the EPF model in ASD. Further, the study of auditory perception in ASD serves as a complementary lens to more symptom-based studies, and helps to better understand individual differences in ASD.