habituation

The weakening or disappearance of an individual's initial spontaneous reaction to a stimulus (eg alertness, defence, attack) as a result of the stimulus occurring repeatedly without any interesting consequences. Changes in the form or consequences of the stimulus may cause the habituated response to reappear.

In psychology, habituation is an example of non-associative learning in which there is a progressive diminution of behavioral response probability with repetition of a stimulus. 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. 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).

However, not all habituation in more complex animals is conscious - 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.

Habituation is stimulus specific. It functions like an average weighted history wavelet interference filter reducing the responsiveness of the organism to a particular stimulus.

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