Dyslexia is a subject that belongs to the study field of learning disabilities, and its cause is widely accepted to be neurological or genetic. Some researchers blame a supposed neurological dysfunction on brain damage incurred before, during, or after birth. Others hold that the neurological dysfunction is genetically determined and inherited from generation to generation.
They support this view by referring to many studies indicating that there often is a family history of learning disabilities. Dr. Beve Hornsby, for example, found that 88% of dyslexics had a near relative who had similar problems with reading and spelling.
According to an American study the risk that a child will have a reading problem is increased from 4 to 13 times if one of the parents has a similar problem. The tendency for dyslexia to “run in families” has been confirmed by numerous studies.
One should, however, never lose sight of the fact that statistical evidence is often no more than circumstantial in nature. Circumstantial evidence must always be interpreted. Unfortunately it can easily be misinterpreted.
It may be useful to present an example of how unwise it can be to base conclusions on statistics only. Until a few decades ago, the inhabitants of some towns in South Africa were allowed to use well water for domestic purposes. In some of these places, the water, when used as drinking water, caused a discolouring of the front teeth. Except in the case of a person with dentures, all the members of the family — father, mother and children — would then have discoloured front teeth. The concordance must have been 100 percent. As already indicated, however, the discolouring of the teeth was not caused by genetics, but by the circumstances which the family shared (i.e., that they all drank the same water).
Another example of the circumstantial nature of statistics is the fact that children raised by English-speaking parents speak English, children raised by Spanish-speaking parents speak Spanish, and children raised by French-speaking parents speak French. Except for exceptional cases where children do not learn to speak at all, the concordance would be 100 percent. Surely nobody would attribute this fact to heredity, but to the fact that a child learns to speak the language (or sometimes languages) which he hears on a daily basis.
It should be noted that, unless they speak to him in Spanish, the child of the English-speaking parents will not be able to speak Spanish, not because there is anything wrong with him, but simply because his parents did not teach him to speak Spanish. The inability to speak Spanish will also run in the family, but is certainly not genetic.
The fact that dyslexia often runs in families is therefore not necessarily caused by genetics, but can also be caused by the fact that the family members share the same unique environment. Of course such problems can also be the result of learning, or the lack of it.