In 1954, psychologist James Olds and his team were working in a laboratory at McGill University, studying how rats learned. They would stick an electrode in a rat's brain and, whenever the rat went to a particular corner of its cage, would give it a small shock and note the reaction. One day they unknowingly inserted the probe in the wrong place, and when Olds tested the rat, it kept returning over and over to the corner where it received the shock. He eventually discovered that if the probe was put in the brain's lateral hypothalamus and the rats were allowed to press a lever and stimulate their own electrodes, they would press until they collapsed.