Can we tell whether our beliefs and judgments are correct or wrong? Results across many domains indicate that people are skilled at discriminating between correct and wrong answers, endorsing the former with greater confidence than the latter. However, it has not been realized that because of people’s adaptation to reality, representative samples of items tend to favor the correct answer, yielding object-level accuracy (OLA) that is considerably better than chance. Across 16 experiments that used 2-alternative forced-choice items from several domains, the confidence/accuracy (C/A) relationship was positive for items with OLA >50%, but consistently negative across items with OLA <50%. A systematic sampling of items that covered the full range of OLA (0–100%) yielded a U-function relating confidence to OLA. The results imply that the positive C/A relationship that has been reported in many studies is an artifact of OLA being better than chance rather than representing a general ability to discriminate between correct and wrong responses. However, the results also support the ecological approach, suggesting that confidence is based on a frugal, “bounded” heuristic that has been specifically tailored to the ecological structure of the natural environment. This heuristic is used despite the fact that for items with OLA <50%, it yields confidence judgments that are counterdiagnostic of accuracy. Our ability to tell between correct and wrong judgments is confined to the probability structure of the world we live in. The results were discussed in terms of the contrast between systematic design and representative design.