Investigating Visual and Auditory Discrimination in Children with High Functioning Autism Spectrum Disorder

Introduction: Autism spectrum disorder (ASD) is a developmental disorder characterized by atypical social interactions and repetitive behaviors. The former trait is hypothesized to be partly caused by unconventional visual and auditory categorization (Church et al., 2010). When presented with novel stimuli, children with ASD do not generalize previous learning like typically developing (TD) children (Mercado & Church, 2016). This predisposition to abnormal category learning has been hypothesized to reflect impaired perceptual learning (Mercado et al.,2021), so it is worth investigating whether this effect extends to discrimination learning. Current literature suggests people learn to discriminate better when stimuli are presented in progressive (easy to difficult) order (Church et al., 2013). 

Purpose:  To explore perceptual discrimination learning in both the visual and auditory modalities. We explored whether children with high functioning (HF) ASD also benefit from a progressive presentation order, and whether they can learn from exposure as well as direct training. 

Methods:  Children with HFASD completed auditory and visual discrimination tasks. For each sensory modality there were four tasks. Each task had a learning and testing phase. Half of the learning phases implemented direct training and the other half mere exposure. Half of the learning phases present stimuli in a random order while the other half in a progressive (easy to difficult) order. In the visual task, the participants decided if a pixelated box had more or less pixels of a specific color. In the auditory task, they determined whether auditory sweep trains had more or less flutters (i.e., changes in the degree of harmonic saturation). 

Results: In the auditory task, children with HFASD showed enhanced learning when stimuli were presented in progressive order whether learning occurred from direct training or mere exposure. In the visual task, children with HFASD did best when stimuli were presented in progressive order when trained. However, they did not show a progressive advantage when they were exposed during the learning phase. 

Conclusions:  Children with HFASD show normal perceptual learning in auditory discrimination but may be impaired in visual tasks. This may explain why they have impaired social development but normal language development.