Within a month, 50 percent of the rats not shocked had died, and the other 50 percent of the no-shock rats had rejected the tumor; this was the normal ratio. As for the rats that mastered shock by pressing a bar to turn it off, 70 percent rejected the tumor. But only 27 percent of the helpless rats, the rats that had experienced uncontrollable shock, rejected the tumor. Madelon Visintainer thus became the first person to demonstrate that a psychological state—learned helplessness—could cause cancer.
