that is over his capacity to store that excess energy and to give feedback.
That very capacity may be developed, thus expanded, by your controlled feeding of praises, so it gets exercised by his longing for your praises.
He never got a chance to long for your praises because it's been in abundant supply by you.
A child's emotional needs is part nature part nurture. Your child may be just less emotional by nature. He may be highly intelligent (going to Brown is a proof) and his mind is filled with thoughts, left little room for emotions. God is fair, if He gave you more of this, He will give you less of that.
It is frustrating to have a child who eschews communicating with you, after you have done so much for him. Consider that part of the price you've paid raising him, you might have done just too good of a job.
(Another way to illustrate the same point. When your baby cries, do you pick him up right away so that he'll stop crying, or you let him cry for a while before picking him up?
When he cries, he is talking to you (not suffering as often misconstrued.) If you don't give him a chance to cry, i.e., to talk, you are depriving him the chance to expand his lung capacity and the energy level to verbally communicate later on.)