The unconditioned stimulus (US) does not involve any prior learning, but still produces a reaction. It is followed by an unconditioned response (UR) that is inevitably produced by the original stimulus. The conditioned stimulus (CS) is a previously neutral stimulus that ultimately elicits a response after being paired with the unconditioned stimulus. Finally, the conditioned response (CR) is the learned response to the conditioned stimulus once a connection exists between the conditioned and unconditioned stimulus (King, 2004). In Pavlov's experiment, food was the unconditioned stimulus and salivation was the unconditioned response. Over time, the dogs established the connection with the bell, which became a conditioned stimulus. Saliva then became the conditioned response. A main characteristic of classical conditioning is that it is involuntary. Is Pavlov's dog experiment still relevant? Over a century later, “Pavloean learning” is still applicable to modern society. However, there is much more to classical conditioning than simply measuring digestive enzymes. Because classical conditioning is an automatic response to the human body, you don't always recognize that you've learned it. Some forms of this learning are innate, while others come from