One theory is that the area of the brain damaged regulates the flow of information within the brain. Because the creative person has less regulation of this information, they receive more of it and are able to combine highly disparate pieces of information into new ideas and inventions. Therefore, ADD is caused by a neurological defect. Another very flippant argument. There are neurological differences between boys and girls, too.
Girls tend to do better at some things and worse at other things than boys.
For any increase in ability there is typically an equal decrease in some other ability. Every adaptation is a tradeoff. But both brain types are normal. Scientists argued for a long time that women were intellectually inferior, and they used their evidence of neurological differences as an argument. Now the same argument is being used again by the medical community to prove that ADDers are inferior.