The prefrontal cortex is crucial for the ability to regulate thought and control behavior. In humans, the development of the cerebral cortex is characterized by an extended period of maturation during which young children exhibit marked deficits in cognitive control. We contend that prolonged prefrontal immaturity is, on balance, advantageous and that the positive consequences of this developmental trajectory outweigh the negative. In particular, we argue that cognitive control impedes convention learning, and that the delay in prefrontal maturation is a necessary adaptation for human learning of social and linguistic conventions. We conclude with a discussion of recent observations that are relevant to this claim in a wide-range of research areas, including creativity, sleep, autism spectrum disorders, and the Flynn effect.