Tomasello et al. have not characterized the motivation underlying shared intentionality, and we hope to encourage research on this topic by offering comparative paradigms and specific empirical questions. Although we agree that nonhuman primates differ greatly from us in terms of shared intentionality, we caution against concluding that they lack all aspects of it before other empirical tools have been exhausted. In addition, identifying the conditions in which humans spontaneously engage in shared intentionality, and the conditions in which we fail, will more fully characterize this ability.