Conjunction fallacy (CF) is an irrational judgment of human intuition. CF is not only an erroneous response using heuristics but also the effects of misunderstanding the task. This study examined the differences of representations depending on the comprehension of the CF task (also called the Linda problem), and investigated when and how these differences occurred. In Experiment 1, participants had to read a passage, answer related questions, and recall the passage incidentally. The results

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... cated that the participants' recall performance of question statements in the Linda problem, which conflicted with heuristics, predicted the CF proportion. In Experiment 2, a new task was conducted to emphasize the sentence in question statements of the Linda problem, and the emphasized effects were compared with Experiment 1. The results from Experiment 2 replicated Experiment 1, and the effect of the modification was shown regardless of whether or not the answers used CF. It shows that participants who answered using CF did not misunderstand the meaning of the question sentence in the task comprehension phase. In Experiment 3, to examine whether the results of Experiment 1 reflected the memory transformation based on rationalization of the participant s answer in the recall phase or the task comprehension substitution based on heuristics in the judgment phase, the recall performance was compared between the CF task and the task that could be answered correctly using heuristics. The results revealed that the difference in the recall performance of the question sentence depended on using heuristics. These findings suggest that CF occurrence was predicted by comprehension of the question (Experiment 1), while difference in comprehension representation arises when making heuristic judgments (experiments 2 and 3). This study not only provides new data on CF occurrence and mechanisms but also suggests the importance of considering the relationship between task comprehension and heuristic judgment.