The devil you know is better than the devil you don’t. This mantra describes how people prefer options with fewer unknowns and avoid options with less information. Consider a patient with brain cancer that has to make a treatment decision with her doctor. The first option is the radiation therapy. This is a more traditional treatment with plenty of data available. Although outcomes are never certain, the patient can establish some expectations based on her age, general health, and tumor type and location. The doctor gives her approximately a 50% success rate of halting the growth and spread of the tumor.

The second option is an experimental surgery she qualifies for. There is no reliable data on this treatment yet, but the doctor says that the surgery could potentially eliminate the tumor completely. However, he is unable to provide a reliable probability of success and unforeseen complications she might experience during or after the surgery. In this case although the patient has the potentially high benefit of eliminating brain cancer with surgery, the high degree of uncertainty leads the patient to choose the radiation treatment instead.