What do you have? Nothing?

[GeoffM]

It may or may not drive us crazy.

In these 2 instances, here is what I feel.

The person who says nothing, it is the other person's responsibility to make that person show the hand, or muck it. If they are going to say they have nothing, then they have to do one or the other. It is obviously his/her turn to show and cannot just say "I have nothing", he or she must react by showing the hand or mucking it.

In the other instance, I say the board speaks for itself. When someone says they have a pair of aces, it is quite obvious that they also have the pair that is face up, so I can see why saying I have a pair of aces is good enough. I actually do this myself, since it is common sense that you have 2 pair.