  Human ecological success relies on our characteristic ability to flexibly
self-organize into cooperative social groups, the most successful of which
employ substantial specialization and division of labor. Unlike most other
animals, humans learn by trial and error during their lives what role to take
on. However, when some critical roles are more attractive than others, and
individuals are self-interested, then there is a social dilemma: each
individual would prefer others take on the critical but unremunerative roles so
they may remain free to take one that pays better. But disaster occurs if all
act thusly and a critical role goes unfilled. In such situations learning an
optimum role distribution may not be possible. Consequently, a fundamental
question is: how can division of labor emerge in groups of self-interested
lifetime-learning individuals? Here we show that by introducing a model of
social norms, which we regard as emergent patterns of decentralized social
sanctioning, it becomes possible for groups of self-interested individuals to
learn a productive division of labor involving all critical roles. Such social
norms work by redistributing rewards within the population to disincentivize
antisocial roles while incentivizing prosocial roles that do not intrinsically
pay as well as others.
