A cognitive bias is a mental error caused by our simplified information processing strategies. Cognitive limitations cause people to employ various simplifying strategies and rules of thumb to ease the burden of mentally processing information to make judgments and decisions. These simple rules of thumb are often useful in helping us deal with complexity and ambiguity. Under many circumstances, however, they lead to predictably faulty judgments known as cognitive biases. Cognitive biases are categorized as biases in evaluation of evidence, biases in perception of cause and effect, biases in estimating probabilities, and hindsight biases.