Our job as a parent is to expose our children to a variety of activities and interests. While we may find one child interested in reading or math – another child may have a passion for one particular sport or activity like horseback riding or nature. Some children will thrive with competition and teams while others would rather do something by themselves. The martial arts if taught in a manner that does not promote competition may be a perfect fit for someone who does not want to compete. If we are not sure where their head is at, we can keep trying by listening to them and paying attention to what appears to make them happy. Then you can do what you can to expose them to and promote their interest.
One word of warning though. Not all children will be interested in the same things and certainly not interested in what the parents may want them to be interested in. Trying to find what our child is passionate for calls for a certain amount of non-ownership, allowing the child to express themselves and then doing what you can to support their interest.
One small side note: One of my children, the youngest, showed an interest in books and films. He would spend hours reading and watching films. As he was exposed to that world more and more he eventually went to college for creative writing and now has a book published. I can tell you that understanding the level of that passion and watching him go to a college for writing is hard for a parent – but one that has resulted in a very happy young adult.