Bob's one brain fertilizer has been music. A brain scan would almost certainly reveal heightened activity in the relevant regions. A normal brain, a better than normal brain. If only ...  

Most likely, Bob has lived with his parents all his life. It is an artificial world, with artificial conventions. Bob knows his way around in this world. His brain circuits have him covered in that department. He knows how to please his parents, even impress their friends.

I can see it now, Bob at the keyboards. Perhaps he is playing in the privacy of his room, but his mom and her friend can clearly hear him from downstairs. He knows they are talking about him, saying nice things about him. He breaks off a tune just in time to hear his mom enunciate with exaggerated precision, "... and he also plays four saxophones."

"Four saxophones," the friend responds with forced enthusiasm. "He is so gifted."

"Four saxophones." Bob's brain is encoding a new memory. Neurons are firing up, laying down new roadwork, associating the memory with warm fuzzy feelings, connecting with other neurons in anticipation of the big day when ...

Poor Bob. He never stood a chance.