Payments and discounts incentivize participation in many transactions about which people know little, but can learn more --- payments for medical trial participation, signing bonuses for job applicants, or price rebates on consumer durables. Who opts into the transaction when given such...

Research provides some observations about learning from events that appear to be rare or quite unusual. All learning has uncertain consequences, but learning from rare events is especially problematic. Learners see many idiosyncrasies and exogenous interference, tendencies that suppress learning...