When Skinner was twenty-four years old, he enrolled in the psychology department of Harvard University and began his studies under William Crozier, the chair of the new physiology department. Though not himself a psychologist, Crozier was interested in studying the behavior of animals “as a whole,” an approach that was different than the approaches that psychologists and physiologists took at the time. Instead of trying to figure out all of the processes that were occurring inside the animal, Crozier—and subsequently Skinner—was more interested in the animal’s overall behavior. Crozier’s ideology matched perfectly with the work that Skinner wished to pursue; he was interested in learning how behavior was related to experimental conditions. Skinner’s most significant and influential work, the notion of operant conditioning and the invention of the operant conditioning chamber, came out of his days at Harvard. The work Skinner conducted while at Harvard University is still some of the most important research with regards to behaviorism—work which he taught firsthand to generations of students at his alma mater until he passed away at the age of eighty-six, in 1990.