Example developmental trajectories which can be expressed within the proposed modelling framework.

Colours correspond to societies and line types correspond to intra- and inter-ethnic sharing rates within each society. At age zero, all participants are expected to behave identically. By adulthood, each society is expected to have distinct intra- and inter-ethnic sharing norms. The change between these endpoints can happen at different ages and different rates across both society and condition. Here, BaYaKa children acquire norms suddenly (blue curves) while Bandongo norms shift more gradually (red curves).