Autism in Preschoolers: Altered Sound Processing

Preschoolers with Autism Show Reduced Neural Response to Approaching Sounds

A new study finds that young children with autism spectrum disorder (ASD) process the context of sounds differently than their peers. Researchers from Boston University and other institutions used EEG to measure brain activity in 67 children aged 3-4 years. They discovered that children with ASD did not show the typical, heightened neural response to sounds that seem to be getting closer, a basic perceptual bias present in other groups.

Testing the “Looming Bias” in Young Children

Lead author Mengxuan Shao and colleagues investigated a fundamental auditory phenomenon: the looming bias. This is the human tendency to prioritize sounds that increase in intensity, as if an object is moving toward us. It’s considered an adaptive survival mechanism. The team wanted to see if this basic form of integrating a sound’s simple feature (rising intensity) with its spatial context (approaching) is altered in young children with ASD, who often report auditory hypersensitivities or differences.

The study included three groups: children with ASD (n=21), children with sensory processing concerns but not ASD (SPC, n=16), and children with typical development (TD, n=30). While seated for an EEG, the children listened to simple tone sequences that either rose in intensity (looming) or fell in intensity (receding). The researchers focused on an early brainwave component called P1, which reflects initial cortical processing of sound.

Missing Neural Signature in Autism Group

The EEG data revealed a clear pattern. Both the TD and SPC groups exhibited the expected looming bias. Their P1 amplitude was significantly larger when they heard the looming stimulus compared to the receding one (TD: t(64) = 6.87, p < .001; SPC: t(64) = 4.07, p < .001). In contrast, the ASD group showed no significant difference in P1 response between the two sound types (p = .194).

The team then calculated a Rise-Fall Difference Score (RFDS) to quantify how much each child’s brain differentiated the sounds. A direct comparison showed the ASD group had a significantly lower RFDS than the TD group (Z = -3.00, padj = .008). This indicates a flatter, less context-dependent neural response profile. The brain responses of the SPC group fell between the ASD and TD groups and were not statistically different from either.

Implications for Understanding Auditory Processing in Autism

The absence of the neural looming bias in preschoolers with ASD points to an early alteration in how the brain uses context to shape basic auditory perception. Senior author A. R. Levin and the team suggest this reflects “altered context-dependent modulation of sensory input.” In practical terms, the brain’s auditory system in ASD may be less influenced by the surrounding acoustic scene, potentially processing individual sounds in a more isolated manner.

This finding may help explain certain auditory experiences reported in autism. A reduced ability to automatically prioritize approaching sounds could contribute to difficulties filtering background noise or an overwhelming sense that all sounds have equal salience. It provides a possible neural basis for symptoms like hyperacusis or auditory overwhelm in some individuals with ASD.

The study has important limitations. As a preprint, it awaits formal peer review. The sample size is modest, and the use of simple tones does not capture the complexity of real-world sounds. The work also cannot determine if this neural difference is specific to autism or represents a broader pattern seen in various neurodevelopmental conditions. Future research will need to confirm these results and explore their link to behavioral sensory symptoms.

Source:
EEG responses to auditory stimuli are less context-dependent in preschoolers with autism spectrum disorder compared to typical development (medRxiv preprint, 2026-04-25)