There are only 2 words that fit grammatically (and provides the parallelism you're looking for): "computers" or "mind," but the problem is that I'm not sure that either of these makes any sense. Is there a sentence before or after this one that could provide more context and more clarity?
I wish I could help, but I'm afraid you're first instinct was correct: it has to be "computers" or "mind," but I can't figure out which it might be because neither makes much sense. In this context, how could the sharpest mind develop the cleverest mind? (A sharp mind usually IS already a clever mind). Maybe the word should be "computers: I suppose the sharpest mind could develop the cleverest computers (with the aid of the new computer)??? sorry--I'am at a loss for further clarification.