Some children with dyslexia have auditory processing disorder

Research in many countries, including NZ, Australia, the UK and the US, has shown that a significant proportion of children with reading disorder have an auditory processing disorder (APD).

An APD can make it difficult to accurately discriminate sounds, especially in difficult listening situations.

Auditory discrimination difficulties in children with APD may lead to reading difficulties, or alternatively auditory processing and reading difficulties may co-occur, or both these problems may be linked to a common underlying deficit, which is yet to be determined.

The term “phonology” refers to the way speech sounds are organised and processed in the brain. Different children may find it easy or difficult to organise, manipulate and use their knowledge of sounds or the sound system to facilitate literacy development.
Phonology is not the same as “phonetics” which refers to the sounds of speech and how they are produced.

A child with a phonology disorder may be able to produce all the sounds in their native languages, but may have difficulty combining sounds appropriately to form words or breaking down the sounds in words.

A phonological deficit will make it difficult for children trying to learn the relationship between letters and speech sounds (“grapheme to phoneme” mapping), and hence a phonological deficit is thought to be one of several possible causes of dyslexia.
Although it is hard to prove a causal link between auditory and/or phonological difficulties and reading problems, these difficulties clearly co-occur in many children.

Research at the University of Auckland has shown an overlap between APD and reading problems. In one study, 42 per cent of children who presented with suspected auditory deficits had APD as well as reading and language difficulties.

A randomised controlled trial of different treatments for APD conducted with these children by Dr Mridula Sharma and Drs Purdy and Kelly showed that auditory discrimination training and language therapy produced significant improvements in phonological awareness and nonword reading.

A “meta-analysis” of the literature conducted in 2003 by Dr Franck Ramus showed that, across 10 different studies exploring the link between auditory processing disorder and dyslexia, 39 per cent of adults and children with dyslexia also had poor auditory processing.

Interventions that are effective for APD, such as auditory training, language therapy and personal FM systems, may be beneficial for some children with dyslexia.
In order to determine the best intervention approach, children with persistent reading difficulties should be assessed by a range of professionals, including a speech language therapist, audiologist and educational psychologist.

For more information contact Dr Jennifer Smart, Dr Andrea Kelly or Dr Suzanne Purdy at the University of Auckland
[audiology@auckland.ac.nz].