In psychology, heuristics are simple, efficient rules which people often use to form judgments and make decisions. They are mental shortcuts that usually involve focusing on one aspect of a complex problem and ignoring others.[1][2][3] These rules work well under most circumstances, but they can lead to systematic deviations from logic, probability or rational choice theory.[citation needed] The resulting errors are called "cognitive biases" and many different types have been documented. These have been shown to affect people's choices in situations like valuing a house or deciding the outcome of a legal case. Heuristics usually govern automatic, intuitive judgments but can also be used as deliberate mental strategies when working from limited information.