Sentence:  "Certainly there is nothing wrong with Alvin's intelligence, but many of the things that should concern him seem to be a matter of complete indifference. On the other hand, he shows a morbid <WSD>curiosity</WSD> regarding subjects which we do not generally discuss." 
Meaning of the word marked with <WSD> tags:  (uncountable) Inquisitiveness; the tendency to ask and learn about things by asking questions, investigating, or exploring. (from 17th c.)