Children's competence or adults' incompetence? Different developmental trajectories in different tasks

Research has shown that adults often make judgments inconsistent with the laws of probability. Furthermore, some studies have shown that children seem to reason better than adults in typical judgment tasks. Classical theories of cognitive development cannot explain these counterintuitive findings. Dual-process theories attempt to account for these findings by proposing two distinct systems of reasoning. Research exploring the development of the two systems, however, has yielded inconsistent results. The purpose of this research is to shed light on factors that have led to such inconsistencies. We expect to identify task-specific factors involved in decision making problems that constitute the reason for conflicting evidence. In Experiment 1 participants were 90 fifth graders, 99 seventh graders and 153 adults. The if-only task was used varying superstitious belief (present or absent). In Experiment 2 participants were 276 fifth graders, 344 seventh graders and 90 adults. The contingency detection problem was used varying: a) probability ratios (equal probability or different probability) and b) superstitious belief (present or absent). In Experiment 1 the age of participants significantly predicts whether they gave a heuristic or a normative response. Interestingly, the heuristic responses increased with age, suggesting adults are more prone to the if-only fallacy than children. The superstitious belief manipulation did not influence the proportion of heuristic responses. In Experiment 2 the interaction between the age of participants and the probability ratios was significant. When ratios were equal only fifth graders focused on the greater number as having a more probable outcome. Instead, when ratios were different, fifth graders gave a higher proportion of correct responses. The different developmental trajectories observed in these experiments are due to task-specific factors. Understanding development of decision making requires understanding how task properties engage the two reasoning systems.