Working with Walter Cannon, A. L. Washburn used a balloon to show that feelings of hunger are accompanied by "Stomach contractions".
Cannon and Washburn presented the stomach contraction idea which states that we recognize we are hungry while our stomach contracts. In the infamous balloon study, Washburn trained himself to swallow a balloon connected to a tube, the balloon was inflated internal of his stomach. When the balloon became inflated, he did now not feel hungry.