Therefore, many scientists believe that, at least in some individuals, autism may be genetic. Scientists have identified some genes as playing a possible role in the development of autism. Autism is one of the most common developmental disabilities. Individuals are of all races and ethnic and socioeconomic backgrounds. Current estimates suggest that approximately 400,000 individuals in the United States have autism.
Autism is three to four times more likely to affect boys than girls.
Autism occurs in individuals of all levels of intelligence. Approximately 75 percent are of low intelligence while 10 percent may demonstrate high intelligence in specific areas such as math. The most intensive period of speech and language development is during the first three years of life, a period when the brain is developing and maturing. These skills appear to develop best in a world that is rich with sounds, sights, and consistent exposure to the speech and language of others. At the root of this development is the desire to communicate or interact with the world.