This explains special interests pretty well:
Quote:
The apparently ‘restricted’ aspects of restricted interests are at least partly related to pattern detection, in that there are positive emotions in the presence of material presenting a high level of internal structure, and a seeking out of material related in form and structure to what has already been encountered and memorized. Limitation of generalization may also be explained by the constraints inherent in the role of similarity in pattern detection, which would prevent an extension of isomorphisms to classes of elements that are excessively dissimilar to those composing the initial form. In any case, there is no reason why autistic perceptual experts would be any less firm, diligent or enthusiastic in their specific preferences for materials and domains than their non-autistic expert counterparts. However, it must also be acknowledged that the information autistics require in order to choose and generalize any given interest is likely to be atypical in many respects (in that this may not be the information that non-autistics would require), and may not be freely or at all available. In addition, the atypical ways in which autistics and savants learn well have attracted little interest and are as yet poorly studied and understood, such that we remain ignorant as to the best ways in which to teach these individuals (Dawson et al. 2008