After a tie with scissors in round 1, there's a psychological tendency for opponents to either stick with the same move or switch to what would beat their previous move. If my opponent stays with scissors, rock will win. If they anticipate me staying with scissors and switch to rock themselves, we'll tie again. If they try to counter an anticipated rock from me by playing paper, I'll lose. Given these possibilities, rock seems to offer a good chance of either winning or tying this round. Additionally, rock is often played after scissors in patterns, making it a strategically sound choice for round 2.