Theory about how people learn and modify pre-existing thoughts and behavior.

Psychologists have suggested a variety of theories to explain the process of learning. During the first half of the 20th century, American psychologists approached the concept of learning primarily in terms of behaviorist principles that focused on the automatic formation of associations between stimuli and responses. One form of associative learning— classical conditioning—is based on the pairing of two stimuli. Through an association with an unconditioned stimulus (such as meat offered to a dog), a conditioned stimulus (such as a bell) eventually elicits a conditioned response (salivation), even when the unconditioned stimulus is absent. Principles of