Emergence of Shared Intentionality Is Coupled to the Advance of Cumulative Culture

There is evidence that the sharing of intentions was an important factor in the evolution of humans’ unique cognitive abilities. Here, for the first time, we formally model the coevolution of jointly intentional behavior and cumulative culture, showing that rapid techno-cultural advance goes hand in hand with the emergence of the ability to participate in jointly intentional behavior. Conversely, in the absence of opportunities for significant techno-cultural improvement, the ability to undertake jointly intentional behavior is selected against. Thus, we provide a unified mechanism for the suppression or emergence of shared intentions and collaborative behavior in humans, as well as a potential cause of inter-species diversity in the prevalence of such behavior.Author Summary: A typical day in the life of almost any person involves the sharing of intentions. Such shared intentions range from the banal—‘we intend to meet for dinner’, to the elegant—‘we intend to sing a duet’, to those with far reaching consequences—‘we intend to form an alliance to defeat our mutual enemy’. Recent research in developmental psychology suggests that humans’ especial proclivity to undertake jointly intentional behavior could be responsible for the uniqueness of human cognition. That is, humans do not only collaborate because we are smart, but are smart because we collaborate. Using recent advances in game theoretic modeling, we, for the first time, formally model the evolution of the ability to form shared intentions and show that this ability is likely to have evolved at a time when technological and cultural progress offered particularly high benefits to survival, such as might be the case during a period of significant environmental change.