I just finished reading a book by Temple Grandin, a high functioning autistic woman who is also a collage professor. Autistic people have difficulty processing all sorts of input from touch, light, auditory and all the ways the brain receives input and attempts to deal with reality. What was a surprise to me is the number of people so affected in major or minor ways. For example, some autistic people don't here hard consonants such as the letters c, p or b and therefore miss much of what is spoken and may thus appear stupid or unable to engage with others. So many steps have to go right in producing a normal person it is sort of surprising so many are normal or near normal.