In a task choice situation, why do some students spontaneously choose challenging tasks while others do not? In the study, 114 undergraduate students were first asked of their perceived competence and interest in solving number puzzles at both individual and situational levels, and then asked to choose one puzzle from four difficulty levels. They received no performance feedback throughout the session. Regression analyses indicated that the students with higher individual interest levels chose more challenging puzzles, while the students with higher levels of perceived competence and low levels of individual interest did not necessarily choose difficult puzzles. The students who chose more challenging puzzles attributed their choices to interest rather than perceived competence. The study suggests a limitation of relying on students' self-reported confidence in their ability and the importance of conceptualizing individual interest as the reason behind the choice of challenging tasks in a low-pressure task choice environment.