Communication via signaling is widespread among a large variety of animals.
Signaling between individuals who have perfectly coinciding interests has
been regarded as self-explanatory, while situations without such perfect
agreement are more puzzling. In these later cases there is sometimes
incentive for signalers to "lie," but they don't. These later cases have
traditionally been explained in terms of signal cost; lying does not occur
because the cost one has to pay to lie outweighs the gain one gets from lying.
Recent work, using different methods, has called into question two of the
primary assumptions in this literature. First, some explanation is required
even in cases where the creatures have perfect overlapping interest --
evolution is far from guaranteed. Second, signal cost may explain one mystery
(the absence of lying), but does so by introducing another (how honest
signaling evolved in the first place). This tutorial will give a brief
overview of this literature and discuss a large collection of open problems.