Confidence is essential to make our decisions, but, is easily affected by other sources, even though sources were unrelated with the target judged. In this paper, We investigated how difficulty of the prior items influence retrospective confidence (RC) and how confidence formed by the difficulty of prior item affect difficulty choice for the next target question. In addition, I observed that lowering the relatedness between the prior and target item can get rid of the effect of prior difficulty. In the result, when the task type between prior and target item are the same, RC was affected by prior item difficulty but, as task type of the target item was changed, this effect disappeared. The level of difficulty of the prior item influenced to choose the difficulty of the target item and the results appeared differently according to the degree of association between prior and target items.
