It’s not about intelligence, it’s about social skills.
As you interact with a person with autism they may look away or barely acknowledge your presence.
The autistic mind works as well as the non-autistic mind, the difference is focus. While most people can split their focus and attention to several things at once, the autistic brain seeks out a single subject on which to focus.
When they are focusing on something, there is little room for anything else. The difference between non-autistic focus and autistic focus is the intensity.
This intensity enables them to see and learn things that no one else can. Not every autistic person is an Einstein or Mozart, but both of them had autistic characteristics and would likely have been diagnosed with autism or Asperger's syndrome.
When they are focusing on an area of interest, an autistic person may talk to be polite, try to listen to you for a brief time, then return to their inner world.
That is, until you ask them about their interests. Suddenly, you find yourself speaking to a walking encyclopedia, with knowledge of anything from computer programming, gaming, science fiction or medieval era costuming.
While autistic interests are narrow, once they pick an area to focus on, they will typically study and explore it until they have learned all they can about it.
A child of twelve might have the knowledge of a college professor.
Facts are committed to memory, books are read from cover to cover and sometimes, written.
When a person with autism is focused on an area of interest, it is best to support them and give them the privacy and space they need.
Special interests are natural and healthy and should be encouraged. They can be used to help autistic children and adults to build social skills and learn new things.
As the interest grows and evolves, the autistic can amass a great deal of knowledge. This is how new ideas come about, and new things are invented.
When you ask an autistic person what they are interested in, do not expect a short unabridged answer.
Ask away! It’s a great way to open a channel of communciation, and you will probably learn something new.
Just make sure you have paper for note taking, you will need it.