Humans routinely confront situations that require coordination between individuals, from mundane activities such as planning where to go for dinner to incredibly complicated activities, such as international agreements. Moreover, despite some failure, we frequently succeed in these situations. How did this ability arise, and what prevents success in those situations in which it breaks down? To understand how this capability has evolved, the CEBUS lab utilizes an explicitly comparative approach. For instance, in one line of research we have discovered a correlation between species that respond negatively to inequity and the tendency to cooperate with non-kin outside of family groups. We also find that primates coordinate on economic games, but that Old World primates find better outcomes than do New World primates, indicating a split within the primate taxon. Finally, are particularly interested in how ecology affects cooperation, and so are comparing primates with another highly cooperative species, cleaner fish, to elucidate the ecological pressures that have influenced cooperation. Such studies help us to better understanding the evolution of cooperation in primates, and hence provide insight in to how cooperation works in humans.