Learning is a relatively permanent behavioral change that occurs as the result of experience. The several types of learning differ from one another in the procedures and elements needed to produce learning. To understand learning, it is important to establish what factors are required for it to occur, not to occur, or to disappear (be extinguished).
Changes in responsiveness to stimulus variations can occur in even the simplest organisms on a temporary basis, but these changes are not learning. Changes in responsiveness include sensitization and habituation.
Sometimes the magnitude of responses to stimuli increases after repeated stimulus exposures, a process called sensitization. For example, after a series of car engine problems, a driver may become very alert when there is a change in engine sounds, sounds that might formerly have been ignored.
Conversely, one may become used to a repeated stimulus, for example a radio in the room next door, and become habituated (display decreased responsiveness) to the noise.
Although these changes are temporary and thus not classified by most theorists as true learning, they are recognized changes in behavior. Changes in behavior can occur also when one is very tired or is experiencing a marked change (increase or decrease) in motivation, such as that provided by extreme hunger. These changes in behavioral responsiveness also are not learning; that is, they are not relatively permanent changes in behavior as a result of experience. The basic types of learning include classical conditioning, operant conditioning, contingency learning, and cognitive learning.