The extracts below are from the post by Stephen Parker found here.
“We take no position on whether there are one or more ultimate causes of dyslexia. But we suggest that there is a common denominator in every case of dyslexia… an inability to decode. This is not to say that we claim to have identified the ultimate cause of dyslexia; for this, one would have to push the question one step back and ask why they cannot decode.”  (Gough, P. B., & Tunmer, W. E. (1986).)
Gough and Tunmer concede that the ultimate cause of dyslexia might well be genetic and neurological, but they leave open the possibility that dyslexia could also result simply because the individual has never been taught, properly, how to decode.
The above was written by Gough and Tunmer more than 3 decades ago. Have they taken a step back to ask why kids are unable to decode?
What does Tunmer mean by 'never been taught, properly, how to decode'? Perhaps Stephen Parker can write to Tunmer and provide us with a response.
I wrote to Professor Bill Tunmer and Professor James Chapman of Massey University a decade ago in 2010. I did not get a response from Bill Tunmer but received a courteous response from James Chapman. My email to them were forwarded to them by Ms. Sharon Wright, the school secretary of Massey University. I will post my emails to them and the response from James Chapman in the near future.
I know why a majority of the so-called dyslexics cannot
decode and that is what my blog is mainly about.
It is a fact that a majority of the kids classified as dyslexic are instructional casualties. I learned from my students what it is that they have been wrongly instructed and I have listed them here.
It is rather strange that Tunmer had said in as early as 1986 that there is a possibility that these kids may have not been taught properly how to decode. Reid Lyon had coined the words ‘Instructional casualties’ and yet they could not or refused to think when I wrote to them.
“The question of the role of decoding in reading and that of its place in reading instruction are surely related, but they are distinct questions. We are here concerned only with the first, the question of the connection between decoding skill and reading ability.”  Gough & Tunmer (1986)
The question of the role of decoding in reading is what I have researched since 2004 and wrote to more than 30 professors including Bill Tunmer in 2010.
As mentioned numerous times in my blog posts a majority of kids are unable to decode because they are instructional casualties. Most of these kids subsequently learn to read implicitly using patterns and analogies. You may read my post on patterns and analogies here. Thank goodness for this innate ability as otherwise a majority around the world, and not just 20% of the population, will leave school as functional illiterates.