Only in recent years have developmental psychologists begun advocating and exploring dual-process theories and their applicability to cognitive development. In this paper, a dual-process model of developments in two processing systems—an “analytic” and an “experiential” system—is discussed. We emphasise the importance of “metacognitive intercession” and developments in this ability to override experiential processing. In each of two studies of sunk cost decisions, age-related developments in normative decisions were observed, as were declines in the use of a “waste not” heuristic. In the second study, children and adolescents were presented with arguments for normative and non-normative sunk cost decisions. Following argument evaluation, participants were re-presented the original problems and a set of novel, transfer problems. Results indicated that post-argument improvements were most apparent during adolescence. Age-related improvements were most noticeable on the transfer problems. In general, the findings suggest that the ability to metacognitively intercede (i.e., reflect on arguments; inhibit experientially produced responses) emerges towards middle adolescence. However, even by the end of adolescence, in the absence of significant contextual cues and motivation, this ability is infrequently utilised.