[This study used a matrix game to explore adolescents' and young adults' flexibility of theory of mind (ToM) and to examine whether prediction could promote a person's ToM reasoning when the opponent's level of ToM changed during the course of the game. A total of 202 participants of different ages (13, 16, 19, and 24 years) were presented with the task. Results showed that the ToM flexibility in prediction and decision making was not significantly different across the age groups. A person's flexibility of ToM was better when the opponent's level was stable than when the level changed. It was even more difficult for a person to adapt when the opponent changed from a higher-order to lower-order level. The results showed prediction to be a kind of information clue that would prompt people to think further. It is both feasible and discriminative to explore even higher levels of ToM with matrix games.]