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Two experiments were conducted to replicate and extend previous findings which indicated that judgment bias about the extent of one's own knowledge can be decreased by a de-biasing technique called counterfactual reasoning, that is, having people consider why their answers to questions may be wrong. The results of the two experiments confirm the effectiveness of this technique to decrease bias, by statistically controlling for important variables. The results extend previous findings about its effectiveness, by showing that counterfactual reasoning (a) reduced bias on knowledge questions about a specific subject area and (b) reduced bias on both hard and easy test questions. In addition, the two experiments establish that bias and test performance are inversely related, and a theoretical connection between this relationship and the ubiquitous hard/easy effect in bias research is offered. The results are discussed in terms of decision-making processes and the potentially detrimental effects of bias on test performance and learning in general.