Habituation

Habituation is a form of non-associative learning in which an organism's non-reinforced response to an inconsequential stimulus decreases after repeated or prolonged presentations of that stimulus. For example, organisms may habituate to repeated sudden loud noises when they learn that these have no consequences. Responses that habituate include those that involve an entire organism or specific biological component systems of an organism. The broad ubiquity of habituation across all forms of life has led to it being called "the simplest, most universal form of learning...as fundamental a characteristic of life as DNA". Functionally, habituation is thought to free up cognitive resources for other stimuli that are associated with biologically important events by diminishing the response to inconsequential stimuli. A progressive decline of a behavior in a habituation procedure may also reflect nonspecific effects such as fatigue, which must be ruled out when the interest is in habituation. Habituation is relevant in psychiatry and psychopathology, as several neuropsychiatric conditions including autism, schizophrenia, migraine, and Tourette syndrome show reduced habituation to a variety of stimulus-types both simple and complex.