Adolescents engage in a wide range of risky behaviors that their older peers shun, and at an enormous cost. Despite being older, stronger, and healthier than children, adolescents face twice the risk of mortality and morbidity faced by their younger peers. Are adolescents really risk-seekers or does some richer underlying preference drive their love of the uncertain? To answer that question, we used standard experimental economic methods to assess the attitudes of 65 individuals ranging in age from 12 to 50 toward risk and ambiguity. Perhaps surprisingly, we found that adolescents were, if anything, more averse to clearly stated risks than their older peers. What distinguished adolescents was their willingness to accept ambiguous conditions-situations in which the likelihood of winning and losing is unknown. Though adults find ambiguous monetary lotteries undesirable, adolescents find them tolerable. This finding suggests that the higher level of risk-taking observed among adolescents may reflect a higher tolerance for the unknown. Biologically, such a tolerance may make sense, because it would allow young organisms to take better advantage of learning opportunities; it also suggests that policies that seek to inform adolescents of the risks, costs, and benefits of unexperienced dangerous behaviors may be effective and, when appropriate, could be used to complement policies that limit their experiences.aging | decision making | uncertainty | lifespan A dolescents engage in more reckless, risky, and thrill-seeking behaviors than their younger and older peers (1-3); they have the highest rates of sexually transmitted diseases (4) and criminal behaviors (5) of any age group, and even drive faster than adults (6). The mortality and morbidity rates of adolescents are 200% greater than their younger peers, an increase that has been attributed to higher rates of what are traditionally called "risky behaviors." Whatever psychological features give rise to these behaviors, they do not reflect flawed reasoning capabilities or generally poor decision-making skills-those are much improved in adolescents compared with younger children (7).To protect adolescents from the consequences of their decisions, modern societies deploy a range of tools. Legally enforced age limits on gambling, drinking, driving, smoking, being able to open a bank account, and make medical decisions all limit adolescent engagement in high-risk behaviors. Educational programs inform adolescents of the risks and consequences of their behaviors in the hope that they will limit dangerous behaviors on their own.We know that younger children show risk-related behaviors clearly distinct from those of adults (8-10). Why do adolescents make choices that dramatically increase their morbidity and mortality rates compared with younger children (11)? What feature of their decision making leads to these negative consequences? Do adolescents acquire a taste for risk that fades with age, or is a more subtle process at work?To more fully understand behavior in risky si...