With the first child, the first time she dropped her cup from the highchair, we picked it up, smiling. The second time, we retrieved it again. Around the 10th time, we realized it was a game--how cute! She was training us! She realized we would pick it up for her! What a smart child!
When the second child did it, we smiled knowingly but still picked up the cup a few times.
Third baby watches it land with a thud on the floor, smiles up at us and we simply smile back.