Autistic Children With Speech Onset Delay Show Reversed Bias in Spectral Versus Temporal Auditory Processing

A recent "hierarchical" reinterpretation of the neurological basis of autism suggests that in autism with early language delay, perceptual processing may be favored over the integration of transmodal information. This model is largely based on neuroimaging findings relating to visual processing, but predicts a corresponding reorganization in the auditory modality. The present study provides the first direct psychophysical evidence of a reversed auditory processing bias in children with prototypical autism, characterized by impaired temporal resolution and enhanced spectral sensitivity. Using two matched psychoacoustic paradigms-temporal gap detection and low-frequency frequency modulation (FM) detection-we assessed auditory thresholds in 21 autistic and 23 typically developing (TD) children. Compared to TD peers, autistic children exhibited significantly higher temporal thresholds and significantly lower spectral thresholds, yielding a markedly elevated Auditory Bias Index (ABI) that quantifies a preference for spectral over temporal cues. In the group of autistic children investigated here, enhanced spectral resolution correlated positively with receptive language and nonverbal IQ, whereas temporal resolution was associated with age-related gains and language outcomes. These findings support the hypothesis of an atypical sensory-perceptual hierarchy in autism with speech onset delay and early behavioral atypicalities, with potential implications for alternative, nonsocial pathways to language acquisition.