Procedural learning is impaired in dyslexia: Evidence from a meta-analysis of serial reaction time studies

Jarrad A.G. Lum,Michael T. Ullman,Gina Conti-Ramsden

doi:10.1016/j.ridd.2013.07.017

Abstract

A number of studies have investigated procedural learning in dyslexia using serial reaction time (SRT) tasks. Overall, the results have been mixed, with evidence of both impaired and intact learning reported. We undertook a systematic search of studies that examined procedural learning using SRT tasks, and synthesized the data using meta-analysis. A total of 14 studies were identified, representing data from 314 individuals with dyslexia and 317 typically developing control participants. The results indicate that, on average, individuals with dyslexia have worse procedural learning abilities than controls, as indexed by sequence learning on the SRT task. The average weighted standardized mean difference (the effect size) was found to be 0.449 (CI95: .204, .693), and was significant (p<.001). However, moderate levels of heterogeneity were found between study-level effect sizes. Meta-regression analyses indicated that studies with older participants that used SRT tasks with second order conditional sequences, or with older participants that used sequences that were presented a large number of times, were associated with smaller effect sizes. These associations are discussed with respect to compensatory and delayed memory systems in dyslexia.

Highlights

Individuals with developmental dyslexia have significant difficulties with reading despite appropriate educational opportunities and an absence of intellectual impairments or an identifiable disease or disorder that might otherwise account for the problem (American Psychiatric Association, 2000; World Health Organization, 1996)
We focused on the serial reaction time (SRT) task because this task has been the most widely used to examine procedural learning in dyslexia, with fully 14 studies to our knowledge, and is the best-studied procedural learning task more generally
In this report meta-analysis was used to evaluate the evidence for procedural learning deficits in individuals with dyslexia

Summary

Introduction

Individuals with developmental dyslexia have significant difficulties with reading despite appropriate educational opportunities and an absence of intellectual impairments or an identifiable disease or disorder that might otherwise account for the problem (American Psychiatric Association, 2000; World Health Organization, 1996). Evidence suggests that difficulties with phonological processing may constitute the core impairment in dyslexia, in particular problems with phonological awareness, that is, the ability to identify and manipulate the sound structure of words in a language (Snowling, 2000). Research has revealed a range of impairments and problems in other domains. The relationship between the reading and other co-occurring problems in dyslexia is still unclear. It remains a subject of ongoing debate which, if any, of the cognitive, language, and/or motor impairments may best account for the reading problems in the disorder (Bishop & Snowling, 2004; Rosen, 2003)

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Discussion

Conclusion