Wherever there are organisms, there are signals. Whether you are walking through a forest, sitting in a meadow, or swimming along a coral reef, your senses are bombarded with messages, most of the produced by non-human signallers and intended for non-human receivers. Calls, patterns, colors, fragrances - these are just a few of the modalities by which signals are sent and received.

To a certain degree these signals must be honest, at least on average. After all, if they were not honest, the intended signal receivers would evolve to ignore them. And if signal receivers ignored these messages, they would be useless - and signallers would eventually evolve not to send them. But why do these signals stay honest? In the short run, at least, there would sometimes seem to be advantages to deception.

Much of honest signalling theory can be thought of as an attempt to answer this question. Though the problem is simple to express, the solution is by no means obvious:

In a few pages, we will consider a number of situations in which this problem applies. (Readers who prefer concrete examples may wish to skip ahead to these sections, using the links below.) For example, male peacocks are thought to use costly ornaments to display quality to potential mates. Baby birds may use costly begging calls to display hunger and thereby solicit food from their parents. Watchful gazelles emply costly alarm displays to display their fleetness-of-foot and escape ability to potential predators.

Before considering these examples, however, we will describe the general solution that signalling theory offers in answer to this puzzle.