Figure 4.

Prediction of Unobserved and Future Behavior

Crosses mark those modes (horizontal axis) already observed in given groups (vertical axis). Red-gray: potential unobserved modes of tool use. With prior belief that all negative observations are equally likely to represent present but unobserved modes of tool use, circles give the posterior probability that a given mode is present but unobserved. Red circles denote a posterior probability over 90%. Blue: potential future emergence of tool use. Assuming that negative observations reflect genuine absences, circles give the posterior probability that a given mode will be the next to be observed in a given group. NW, New World; OW, Old World.