Taste aversion is a unique form of classical conditioning where an organism learns to associate the taste of a particular food with a subsequent feeling of illness. This response is notable because it can be established after just a single pairing and with a long delay, sometimes several hours, between consumption (conditioned stimulus) and sickness (unconditioned stimulus). Research suggests this is an evolutionary adaptation that helps organisms quickly learn to avoid harmful foods, contributing to species survival. This understanding is also applied to help manage nausea induced by medical treatments, such as chemotherapy.