Adaptation-Level Theory – is a Theory that pertains to how humans form contrasting judgments between stimuli. The term Adaptation Level is used to refer to an individual’s perceived norm of a stimulus, which, according to this theory, can be estimated by taking the logarithm of the average similarly experienced stimuli.

Therefore, if judging whether a female on a college campus is attractive, a logarithmic function of the females seen and experienced on campus will be used to evaluate the female in question.
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See also: http://www.marketing91.com/adaptation-level-theory/; http://www.oxfordreference.com/view/10.1093/oi/authority.20110803095350211