Boyd and Richerson argue that the evolution of cumulative culture depends on observational learning and is uncommon in other species because it is ineffective when it is rare in a population.

• 博伊德和里查森强调，累积文化的进化取决于观察学习，而累积文化的进化在其他物种中是少见的；因为当观察学习在群体中少见时，观察学习是效率低的。