The neuromodulator dopamine is believed to play multiple roles in decision making, but the neurocomputational basis of dopamine’s influence on behavior remains unclear. Through a combination of fMRI, pharmacology, and smartphone-based experiments in the general population and in Parkinson’s disease, we find evidence that dopamine is associated with increased risk taking in a manner that does not depend on value. Surprising sounds are associated with dopamine release, and we find that surprising sounds increase risk taking in a manner that does not depend on value. Dopamine is also believed to influence willingness to exert effort. We introduce a new task to study the vigor with which actions are taken to obtain reward and the relationship between vigor and mood. We use a combination of lab, online, and smartphone-based experiments to quantify the relationship between reward, mood, and vigor across the lifespan.