Another way of looking at the theories of what causes dyslexia is to understand that all are partial explanations of the large condition that is dyslexia.
Together they form a fairly good understanding of what dyslexia is where they all fail when considered individually.
Granted, each theory has believers that claim " This is dyslexia ". If the goal is to understand a particular dyslexic and get help for that particular dyslexic, then the reality is that it needs to be determined which theory applies to that dyslexic so that a focused intervention can be developed.
There seems to be a disconnect between what dyslexia researchers are trying to do ,which is finding the single cause of dyslexia and what is wanted by most dyslexics which is what intervention will help him or her.
I offer as proof the different studies using fMRI to study dyslexia that study
specific areas of the brain ( generally each of which is related to a particular theory of what dyslexia is ). All the studies find the same result of being able to see the difference between groups of dyslexics and non dyslexics but with data overlap between the groups that makes identifying individual dyslexics impossible.
If you have only read the media reports of those studies and have already picked one that you firmly believe is the right result and that what causes dyslexia has been found , I suggest you find and read the researchers conclusions. Not one researcher can claim to evaluate a person by fMRI and determine if he or she is dyslexic.
When different dyslexics have different problems , which is what is observed, how can one theory of one cause be correct. On the plus side you can conclude that indeed these theories are each and every one of them are supported by fMRI
FOR SOME DYSLEXICS BUT NOT ALL .
I personally have developed filter glasses for the minority of dyslexics that fit the criteria of being able to describe a visual problem that makes reading difficult. While that criteria covers a broad range of visual problems that make reading difficult it is narrow enough so that an individual can determine if he or she is in the group.
My point is that while no one theory covers all dyslexics, together they do form a list of problems from which any particular dyslexic is likely to be able to find the cause of his or her dyslexia problems. What is still needed is for the different interventions to determine criteria that will identify which intervention will help which dyslexic.
Until that happens, dyslexia interventions developed for a particular theory will continue to have failure rates due to the simple fact that some dyslexics have problems in other areas that are not addressed.
