The Theory of Honest Signalling

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Introduction: Part 1

Introduction: Part 2

The Basic Problem

The Basic Solution

Honest signalling in biology

Zahavi's handicap principle

Grafen's model

Attracting mates

Begging for food

Deterring predation

Contesting resources

Autumn color

Honest signalling in economics

Conspicuous consumption


The mathematics of honest signalling

Signalling as a game


Other resources

Carl T. Bergstrom

Using Mathematica

Contact Information

Department of Zoology
University of Washington
Box 351800
Seattle, WA 98195-1800

The Basic Problem

Nearly anywhere that there are organisms, there are signals. Whether walking through a forest, sitting in a meadow, or swimming along a coral reef, one's senses are practically bombarded with messages. 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:

Two individuals have access to different information.

They could both gain if they could honestly share this information.

However, their interests do not coincide entirely, and so each has an incentive to deceive the other.

How can honest communication be ensured?

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.

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Last modified September 4, 2002
Copyright © 2002 Carl T. Bergstrom