Figure 4.

Stable cost-free signaling despite conflict of interest between some signaler–donor pairs. Axes are as in Fig. 1. Consider a signaling system with a stable two-pool cost-free signaling equilibrium, with the boundary between the two pools at S. A signaler at this boundary—represented by point A—would like to receive the resource from the donors in the region a_d but not from those in the region a_n. Therefore, this signaler ideally would choose to be seen by donors as being at point B. However, in this signaling system, there is no signal available that would be understood as indicating quality B; the signalers can either signal that they are needy and be treated as if they have the mean fitness of signalers in the needy pool, N, or they can signal that they are healthy and thus be treated as if they have the mean fitness of those in the healthy pool, H. Although the signalers could deceive the donors in a_dby signaling needy, by doing so they also would deceive the donors in a_n into transferring. This action runs counter to the signalers’ interest because they do not benefit from receiving the resource from these donors. The benefit of deceiving a_d is offset by the cost of deceiving a_n; the signaler at A has no incentive to signal needy. All of the signalers to the right of A will have even more to lose and less to gain by signaling “needy” and therefore will also signal “healthy.” Hence this cost-free signaling equilibrium is stable despite some conflict of interest.