Myomancy ADHD, Dyslexia and Autism

The role of hearing is critical in dyslexia and other learning difficulties. Now a new study is looking at Auditory Processing Disorder (APD) in dyslexia. APD, previously known as Central Auditory Processing Disorder (CAPD), is characterised by problems with:

• Auditory Discrimination; the ability to distinguish between similar sounds or words
• Auditory Figure-Ground; the ability to distinguish relevant speech from background noise
• Auditory Memory, the ability to recall what was heard

Entitled Comorbid Auditory Processing Disorder in Developmental Dyslexia, the study used 11 dyslexic children with 14 non-dyslexic controls. Putting them through a series of trials, the researchers found that dyslexics did badly on the Frequency Pattern Test (FPT) and the Duration Pattern Test (DPT). In the FPT, the subject hears a pattern of three tones that are either “high” (1122 Hz) or “low” (880 Hz), e.g. High-High-Low or Low-High-Low. The subject then repeats the pattern back to the researcher. This tests many skills including detection of the change in tone and the subject’s memory. The DPT is similar but tests the ability to observe and remember the duration of sounds.
Why is this relevant to dyslexia? Imagine you can’t tell or remember the difference between different frequencies of sound. It fairly obvious that you would be bad at music as musical notes are just the same noise but at different frequencies. But why is reading and spelling effected? Have a look at this diagram:

The vertical axis is the decibels or volume and the horizontal axis is the frequency of the sound from 125hz to 8000hz. The grey area represents the range for normal speech with primary vowels, ‘a,e,i.o.u’, at one end and primary consonants, ’s,d,f and so on, at the other end. If someone has problems detecting the difference between frequencies of sound then they have problems hearing the different sounds that make up words so many words sound similar. Normally we learn to read by parents or teachers reading out loud and pointing to the word. If lots of the words sound the same to a child then they cannot make a connection between the words on the page and the words being spoken.
The study concludes “Approximately half of the participants with developmental dyslexia showed clinically significant diminished performance on the FPT and DPT indicative of APD. These results indicate that the percentage of persons with developmental dyslexia and comorbid APD may be substantial enough to warrant serious clinical considerations“.

Also on Myomancy: Cocktail Party Deafness , Background Noise, Dysleixa and Earobics

Further Reading: Three Commonly Asked Questions About Central Auditory Processing Disorders [PDF], The Audiogram: Explanation and Significance