Habituation

Habituation is an example of non-associative learning in which there is a progressive diminution of behavioral response probability with repetition of a stimulus. It is another form of integration. An animal first responds to a sensory stimulus, but if it is neither rewarding nor harmful the animal learns to suppress its response through repeated encounters. One example of this can be seen in small song birds - if a stuffed owl (or similar predator) is introduced into the cage, the birds react to it as though it were a real predator, but soon realise that it is not and so become habituated to it. If another stuffed owl is introduced (or the same one removed and re-introduced), the birds react to it as though it were a predator, showing that it is only a very specific stimulus that is being ignored (namely, one particular unmoving owl in one place). This learned suppression of response is habituation.

However, not all habituation is conscious like this - for example, a short amount of time after dressing, the stimulus the weight of clothes creates is 'ignored' by the nervous system and we become unaware of it. In this way, habituation is used to ignore any continual stimulus, as changes in stimulus level are normally far more important than absolute levels of stimulation. Negative feedback from the brain to peripheral sensory organs inhibits the transmission of the stimulus at the source of the stimulus.

This 'learning' is a fundamental or basic process of biological systems and does not require conscious motivation or awareness to occur. Indeed, without habituation we would be unable to distinguish meaningful information from the background, unchanging information.

Habituation is stimulus specific. It does not cause a general decline in responsiveness. It functions like an average weighted history wavelet interference filter reducing the responsiveness of the organism to a particular stimulus. Frequently one can see opponent processes after the stimulus is removed.

Habituation is connected to associational reciprocal inhibition phenomenon, opponent process, motion after effect, color constancy, size constancy, and negative image after effect.

Habituation is frequently used in testing psychological phenomenon. Both infants and adults look less and less as a result of consistent exposure to a particular stimulus. The amount of time spent looking to a presented alternate stimulus (after habituation to the initial stimulus) is indicative of the strength of the remembered percept of the previous stimulus. It is also used to discover the resolution of perceptual systems, for example, by habituating a subject to one stimulus, and then observing responses to similar ones, one can detect the smallest degree of difference that is detectable by the subject.