Auditory frequency discrimination has been used as anindex of sensory processing in developmental language dis-orders such as dyslexia, where group differences have oftenbeen interpreted as evidence for a basic deficit in auditoryprocessing that underpins and constrains individual variabil-ity in the development of phonological skills. Here, we con-ducted a meta-analysis to evaluate the cumulative evidencefor group differences in frequency discrimination and toexplore the impact of some potential moderator variablesthat could contribute to variability in effect-size estimationsacross studies. Our analyses revealed mean effect sizes forgroup differences on frequency discrimination tasks on theorder of three-quarters of a standard deviation, but in thepresence of substantial inter-study variability in their magni-tude. Moderator variable analyses indicated that factorsrelated both to participant variability on behavioural andcognitive variables associated with the dyslexia phenotype,and to variability in the task design, contributed to differ-ences in the magnitude of effect size across studies. Theapparently complex pattern of results was compounded bythe lack of concurrent, standardised metrics of cognitiveand reading component skills across the constituent studies.Differences on sensory processing tasks are often reportedin studies of developmental disorders, but these need to be more carefully interpreted in the context of non-sensoryfactors, which may explain significant inter- and intra-groupvariance in the dependent measure of interest.
Bibliographical noteThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution andreproduction in any medium, provided the original work is properly cited.© 2019 The Authors.Dyslexia published by John Wiley & Sons Ltd.
Funding: Economic and Social Research Council, Grant/Award Number: ES/H031685/1.
- developmental dyslexia
- frequency discrimination
- phonological awareness