text: History B. F. Skinner first identified and described the principles of operant conditioning that are used in clicker training. Two students of Skinner's, Marian Kruse and Keller Breland, worked with him researching pigeon behavior and training projects during World War II, when pigeons were taught to "bowl" (push a ball with their beaks). They believed that traditional animal training was being needlessly hindered because methods of praise and reward then in use did not inform the animal of success with enough promptness and precision to create the required cognitive connections for speedy learning. They saw the potential for using the operation conditioning method in commercial animal training. The two later married and in 1947 created Animal Behavior Enterprises (ABE), "the first commercial animal training business to intentionally and systematically incorporate the principles of behavior analysis and operant conditioning into animal training."
  The Brelands coined the term "bridging stimulus" in the 1940s to refer to the function of a secondary reinforcer such as a whistle or click. ABE continued operations until 1990, with the assistance of Bob Bailey after Keller Breland died in 1965. They report having trained over 15,000 animals and over 150 species during their time in operation. Their positive methods contrasted with traditional training using aversives such as choke chains, prong collars, leash snapping, ear pinching, “alpha-rolling,” the shock collar, elephant goad, cattle prods, and elephant crushing.