Live class results. Round 1 records what students choose to give. Round 2 samples candidate responses in proportion to their Round-1 survival, without replacement within each pair, then records what users choose to receive.
For each response style, compare its share of Round-1 selections, share of Round-2 exposures, and share of Round-2 wins. Because Round 2 is sampled from Round 1, changes from exposure → win isolate the second selection stage more cleanly.