Pavlov was a Russian physiologist who experimented with conditioning responses. He rang a bell every time that he fed a dog to the point that whenever he rang this bell, the dog would salivate, thinking he would be fed. Thus, Pavlov began the study of conditioned responses and their implications for psychology; this study is termed classical conditioning.
In "Brave New World," the castes are conditioned to think in certain ways through hypnopaedia, sleep-conditioning. For example, Betas are taught to dislike Deltas so that they will not associate with them. This process can also be used for counter-conditioning to get rid of unwanted behavior. Of course, this conditioning works better in "Brave New World" because the individual differences of humans have been eliminated by the genetic engineering in the Hatchery.
A Neo-Pavlovian is a conditioning room where the babies in their different categories are conditions to fit into their life roles in the new world. Each set of babies belong to a specific group and are trained to ensure they conduct the roles as required by their group. In Chapter 2 of the story, the Director takes a group of students to the nurseries to demonstrate how conditioning is achieved. The Director instructs that books and flowers be positioned in front of “Delta” babies. Due to their curiosity the babies crawl happily towards the objects, however when they are just close enough to touch the items, a mild electric shock is delivered to their bodies. The pain forces them to back away, and when they are presented by the items once again the babies are completely terrified. Basically a Neo-Pavlovian is a human conditioned to fit into a specific group or class of people as required in the brave new world.