One of the hallmarks of Asperger's syndrome, is the special interests they develop. Most Aspie's will have something to which they will devote nearly all their time, if given the chance. They will become walking encyclopedias of knowledge in their area of interest. The most common area of interest is probably the weather. I have met Asperger's kids with this special interest. You will say "Hi" to them. They will respond with "There is an interesting cell developing today over NE Kansas. May be some good tornadoes", or something similar. Aspie's do not intuitively understand the need for social conventions. No social niceties. Just jump ahead to the meat of the conversation. As a parent, you will become used to this, but it is hard for others to deal with.
Our son has had a number of special interests. Kerosene lamps was one for a long time. Rocks was another. When we went to the Smithsonian Institute for the first time, we basically stayed in the rock and crystal exhibit for two days. The guards were starting to look at us pretty funny. One of his oddest interests was gas and kerosene cans. He had to carry an empty gas can everywhere with him. He knew everything he could possibly know about different kinds of gas cans and containers. Nothing like walking into an Olive Garden with a child with a gas can. "We brought our own salad dressing" seemed to reassure the waitresses.
Why do they have these interests? No one really knows. My son says it is easier than dealing with people, but also admits he is not sure either. I have wondered if it is a stress reducer. It takes a lot of energy and it is quite stressful spending all day trying to figure out what is going on with other people.
What do we do about them? As a group, Dads are pretty goal oriented. We understand spending extra time on stuff we like, but you have to get other stuff done also. Our natural inclination is to want to reduce the time our kids spend on their interests, so they can be productive or be more like other kids. I would suggest the following.
1) Unconditional acceptance. Moms give unconditional love and Dads give conditional love, as a general rule. I think this is a good thing for our children. It is probably good for our Aspie kids also. Unconditional acceptance simply means that you accept that they have certain core characteristics that you cannot change. You accept those differences and learn to love them for those differences. Your Aspie kid will never quite be like the other kids, but then every child is different in some way.
2)Work with the special interests. Research, and personal experience, has shown that when you try to do away with those interests, these kids become very anxious. Acting out and power struggles ensue. The Asperger's child really does NOT understand why you don't find his special interest just as fascinating as he does. Talk with his/her teachers and tell them his writing endeavors will be about the weather. Have the math assignments involve calculating numbers of clouds or dinosaurs or whatever the current interest may be. With a little creativity, you will have your child learning everything they need to learn AND be enthusiastic about it.
3) Discipline. Disciplining Aspie kids is a whole topic unto itself. On the specific area of special interests, I would suggest that you NOT use that as a tool for discipline. Those interests are important to these kids in ways we just do not understand. It is their obsession. I have made this mistake. I have seen the poor results. Thank God my wife was their to gently correct and help me. Take away their dessert or TV time, like you would the other kids. If they are spending too much time on their interest deal with that as a separate issue, not out of anger as a means of discipline.