Since the opponent has chosen rock twice in a row, there's a possibility they'll continue this pattern. Even if they're recognizing their own pattern and considering a change, they might anticipate that I'll switch to scissors (to beat their previous rock), in which case they might choose rock again. Paper beats rock, so I'll go with paper for this round to capitalize on their potential continued use of rock. This also gives me protection if they attempt to predict my next move based on a pattern.