We use the term "classical conditioning" to describe one type of associative learning in which there is no contingency between response and reinforcer. This situation resembles most closely the experiment from Pavlov in the 1920s, where he trained his dogs to associate a bell ring with a food-reward. In such experiments, the subject initially shows weak or no response to a conditioned stimulus (CS, e.g. the bell), but a measurable unconditioned response (UCR, e.g. saliva production) to an unconditioned stimulus (UCS, e.g. food). In the course of the training, the CS is repeatedly presented together with the UCS; eventually the subject forms an association between the US and the CS. In a subsequent test-phase, the subject will show the conditioned response (CR, e.g. saliva production) to the CS alone, if such an association has been established and memorized. Such "Pavlovian" conditioning is opposed to instrumental or operant, where producing a CR controls the UCS presentations.Therefore, classical conditioning involves learning by association - where you simply learn by associating two events that often occur together. Conditioning, in general occurs more rapidly when the conditioned stimulus in unfamiliar rather than familiar.High order conditioning is when a CS can be used to produce a response from another neutral stimulus (can evoke CS). There are a couple of different orders or levels. Taking Pavlovs dogs as an example, where light is paired with food. The food is a US since it produces a response without any prior learning. Then, when food is paired with a neutral stimulus (light) it becomes a Conditioned Stimulus (CS) - the dog begins to respond (salivate) to the light without the presentation of the food.One of the principles of classical conditioning is extinction. If a CS is repeatedly presented without the unconditioned stimulus, the CR will disappear. In Pavlovs case, if a dog learns to associate the sound of a bell with f...
