The opponent has played paper in the last two rounds (7 and 8), and just won with paper. After a win, players sometimes stick with their winning move, but the repeated use of paper makes it more likely they'll switch to something else. If they switch to rock, I'd lose, but if they stay with paper or switch to scissors, scissors would either win or tie. Since the opponent has shown a tendency to use paper more than other options (4 times out of 8 rounds), scissors gives me the best chance to counter their most frequent choice.