Habituation

Habituation is a form of non-associative learning in which an organism's non-reinforced response to an inconsequential stimulus decreases after that stimulus is presented repeatedly or for a prolonged period, as when an organism learns to stop startling at a repeated sudden loud noise once it carries no real consequence. It occurs across responses involving an entire organism as well as specific biological component systems within one, and its broad presence across essentially all forms of life has led it to be called the simplest and most universal form of learning, as fundamental to life as DNA itself. Functionally, habituation is thought to free up cognitive resources for stimuli that are actually tied to biologically important events, by reducing the response to stimuli that carry no such importance; a general decline in behavior during a habituation procedure can also reflect an unrelated cause such as fatigue, which researchers must rule out before treating the decline as genuine habituation, and the phenomenon is also relevant to psychiatry, since several neuropsychiatric conditions, including autism, schizophrenia, migraine and Tourette syndrome, show reduced habituation.