Procedural Learning in Adults with and without Developmental Language Disorder: The Influence of Manual Motor Demands

Abstract

The purpose of this research project was to determine differences in procedural learning in adults with and without developmental language disorder (DLD) when manual motor output is and is not required for a learning task. DLD is a neurodevelopmental disorder characterized by unexplained deficits in expressive and/or receptive components of language. The Procedural Deficit Hypothesis (PDH) suggests that individuals with DLD possess deficits in procedural learning and memory due to underlying brain structures responsible for both components of implicit learning and linguistic skill. Relatedly, the Sequential Pattern Learning Deficit Hypothesis (SPLDH) proposes that only sequence-based procedural memory and learning is impaired in DLD populations. In the present study, we employed two sequence-based procedural learning tasks to determine the influence of manual motor output demands on procedural learning. A total of 23 participants (4 = DLD; 19 = typical development) engaged in a serial reaction time task (SRTT) measuring their ability to implicitly learn a visually-presented, 10- element sequence via manual motor output (i.e., keystrokes on a keyboard). These same participants engaged in a visual statistical learning (VSL) task to measure their implicit learning when manual motor output is not demanded. Consistent with the PDH and SPLDH, we hypothesized that adults with DLD would perform worse on motor-dependent sequential learning task when compared to adults with typical development, indicating poorer procedural learning and memory when manual motor output is required. However, we additionally hypothesized that adults with DLD would perform similarly to typically developed adults on the sequential learning task in which manual motor output was not required. Here we present initial results on the preliminary data set. Visual inspection of our initial results indicates that the DLD group performs worse on the SRTT and equivalently on the statistical learning task, consistent with our hypotheses. Statistical analysis did not yield significant results with the current sample size. This study contributes to the existing literature by exploring the influence of motor demands on procedural learning in DLD populations. Implications and future directions are discussed.