Does anyone know which book I'm thinking of?

I read this book years and years ago, It was one novel in a compilation of three. I cannot remember the title for the life of me, but I would like to read it again. I remember it was about a man who was born mentally retarded or something of the sort, and because of some type of experiment, a doctor was able to gradually get him to be normal and he became very intelligent. In the initial stages of the experiment, when they were trying to get him used to social life (in school) if he became frightened, he would feel like "an animal that was being preyed on" or something like that. Ugh, I cannot remember and it's driving me crazy! Someone please help if this rings any bells!