Predictably Irrational

How a Hospital Bed Became a Laboratory

When Dan Ariely was eighteen, a magnesium flare exploded next to him. Third-degree burns covered seventy percent of his body. He spent three years in an Israeli hospital wrapped in bandages, his face hidden behind a tight synthetic mask that made him look, he later joked, like a crooked version of Spider-Man. The worst part of every day was the bath. Nurses would soak him in disinfectant, then rip the bandages off his raw flesh. They yanked fast. They were sure that one sharp spike of pain was kinder than a slow build. They had been ripping bandages off burn patients for decades, and they had never questioned the method.

Ariely, lying there screaming, had a different theory. He suspected the nurses were wrong. So when he eventually walked out of the hospital, he went looking for proof. He ran experiments. He held people's hands in ice water and pressed weights on their skin and exposed them to loud noises and even simulated stock market losses. He measured pain. The data was clear. Lower intensity stretched over more time produced less total suffering than a short, brutal jolt. The nurses, with all their experience, had been mistaken about something they did every single day.

That story is the spine of Predictably Irrational. Experts can be wrong in patterned, repeated, foreseeable ways. Ordinary people can be wrong in the same patterned, repeated, foreseeable ways. The mistakes are not random noise around a rational signal. They are the signal. Once you see how systematic our errors are, the entire edifice of modern economics, which assumes humans calculate and choose with cold precision, starts to look like a polite fiction.