Thanks Mana, my son doesn't do any pattern now too, but he still loves star at spinning objects, and he can detect any spinning stuff in the environment. Somehow we believed that his nerves wiring is really so different from us :P

My son does have some friends he like to play with, two are boys (he is a bit scare of girl i think) and both of them speak cantonese, language may be a problem for his social interaction in sch.

Actually when i Google search for obsessive interest, ASD and Giftedness pop up, and this is the first time I think that my son may be ASD or gifted (or both or none :P) In my culture (and in my childhood) we seldom heard about giftedness, so i didn't know anything about it. (I only thought that gifted = Newton/Einstein, etc) Somehow it is really confused for me for my son's intense interest, should I stop him learning his math? or should I follow his lead?

Yup, we are looking for a therapy for him too. ^^