All effective modern animal training has a common basis: the discovery of "operant conditioning" by B.F. Skinner. Assisting in this research were Keller & Marian Breland, graduate students of Skinner who continued to develop the science into a systematic method for training animals. They documented their work in the seminal text, Animal Behavior, first published in 1966 but out of print for decades. This historic book brought the Brelands' research to the world.In 2018, Animal Behavior was republished by Storymakers, Inc. with a slate of historic photographs and a Special Introduction by Dr. Robert E. Bailey, ScD.–esteemed colleague of the Brelands and first Director of Training for the U.S. Navy Marine Mammal Training Program. Dr. Bailey’s introduction provides historic context for the contribution of the Brelands' work to behavior science.