Procedural Auditory Category Learning is Selectively Disrupted in Developmental Language Disorder

Abstract

Developmental Language Disorder (DLD) is presumed to arise due to a malfunctioning procedural memory system alongside a preserved/enhanced declarative memory system. Despite accumulating evidence supporting this notion, there is a major gap in our understanding of procedural learning functions in DLD. Prior research has tended to focus on the impaired outcomes of procedural learning in DLD but has not yet systematically studied the learning process that leads to these differences. Without fine-grained assessment of online processing during learning, it is impossible to ascertain the cause of poorer learning outcomes in DLD. Here we capitalized on perceptual category learning combined with computational models that characterize the strategies employed during learning to unravel the nature of procedural learning disruption in DLD. Children with DLD and typically developed (TD) children completed two well-matched nonspeech auditory category learning challenges to draw upon presumed procedural (information-integration) versus declarative (rule-based) learning systems. We observed impaired information-integration category learning and intact rule-based category learning in the DLD group compared to the TD group. Quantitative model-based analyses revealed reduced use of, and slower shifting to, optimal procedural-based strategies in DLD and slower shifting to but similarly efficient use of optimal hypothesis-testing strategies. The dissociation is consistent with the procedural deficit hypothesis and multiple category learning systems. To the extent that perceptual category learning via procedural memory systems is a basic building block upon which linguistic skills are formed, the present findings promote our understanding of the difficulties children with DLD face in forming stable linguistic representations.