Understanding time investment while solving problems is central to metacognitive research. By the Diminishing Criterion Model (DCM), time regulation is guided by two stopping rules: a confidence criterion that drops as time is invested in each problem and the maximum time to be invested. This combination generates curved confidence–time associations. We compared the belief that intelligence is malleable, a growth mindset, to the belief that intelligence is fixed, and to neutral control groups. We hypothesized that a growth mindset leads people (...) to selectively invest time in problems carrying the hope of improvement. This extra time makes the curved DCM pattern curvier. In two experiments, participants primed with growth, fixed, or control mindsets solved analogies (Experiment 1) and compound remote associates (Experiment 2). As expected, in both experiments a growth mindset exhibited a curvier confidence–time pattern, while the fixed mindset and control groups replicated previous confidence–time associations. Most additional time was invested in problems with intermediate difficulty levels, suggesting strategic time allocation. The study offers useful measures for delving into factors that affect thinking time allocation. (shrink)