What role does left or right handedness play in dyslexia? Some approaches such as
The Dominance Factor by Carla Hannaford argue that learning problems occur when children have mis-matched dominance. For example, right handed but left eyed. The data on this is very confused and no one really knows even the basics such as why are most people right handed but some are left handed?
The two hemispheres of the brain communicate using the Corpus Callosums. A thick bundle of nerves that links the two halves of the brain. Research has shown that its thickness can vary a great deal from person to person suggesting that some people are better equipped for cross-hemispheric communication. What difference does this make and what factors influence the size of the corpus callosum? BPS Research Digest has an interesting article looking at new research in this area.
…the callosum varied little between the sexes or between the left and right-handers (less than 3 per cent difference in each case), but varied significantly according hemisphericity, with right-brain dominant participants having a 10 per cent thicker callosum on average.
Thickness of the callosum was also independently related to something called ‘dichotic deafness’, a common characteristic of people with a left-hemisphere dominant brain . This is the inability of some people to hear two sounds presented simultaneously, when one sound is played to one ear and the other sound to the other ear.
Actually, my son and myself had the dominant eye switched (do NOT try it yourself; there can be non-trivial side-effects). It was part of a therapy to get dyslexia and headaches removed. And, it worked. Dyslexia, headaches (and also ADHD) are essentially cured. But, it probably would not have had this effect, if this would have been the only thing that got addressed. It were multiple inefficiencies that were addressed and this brought the break-through.
The question is, why does switching the dominant eye deliver this result? With my computer background, I can say, it is all a matter of optimum workload placement. If that is not the case, capacity bottlenecks can be expected (Chris, I believe you call it Log Jam Hypothesis). A typical example is when too many cars enter a motorway and stop-and-go occurs. Add a some rain and less cars are needed to create the stop-and-go; close a lane; etc…
The connection between the two hemispheres is a strong candidate for such a bottleneck and there are strong parallels with computers. In large computers, if the path between a disk and the processor is too busy and this creates a bottleneck, we simply move the data to another disk that has a less busy path. This clears the bottleneck. This is standard practice. Surely, something very similar happens when the dominant eye is switched. One wonders, why doesn’t this appear to have the attention of scientists?
Actually, this can be explained at neuron level. For more information see my home page.
Eugen