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Many animals have evolved the use of the "threat display" (also called "agonistic display," "aggressive signaling," "contest behavior" or "ritualized combat"), a stereotypic and sometimes bizarre behavior that allows two opponents to assess each other without the costs of an all-out fight. In many cases, there is a whole sequence of display behaviors, each one a little more costly and challenging, so that if the initial display does not settle the dispute, the opponents move on to another level of display. This sequence of behaviors is called "sequential assessment."

A famous study of "red deer" (also known as elk) revealed that contests between males went through three stages:

1. roaring
2. parallel walk
3. fighting

This diagram shows the progress and outcomes of 50 encounters between males. The size of the arrows represents the number of encounters that took a particular route. Only 14 of the original 50 encounters ended with an actual fight.

"Sequential assessment" is one of many "games" that have been modeled in game theory, a theoretical discipline that seeks to predict how different strategies affect the outcome of a conflict between two opponents. (There are many game-theory-related web sites.)

Sequential assessment is a variant of the "Hawk-Dove" game. In the "Hawk-Dove" game, the two possible strategies are "always escalate to a fight" and "initially display, but run away if opponent escalates." Which of these two strategies is optimal depends on the cost of fighting, and on the value of the payoff. It is assumed that the two opponents are equal in fighting ability.

In the "Hawk-Dove-Assessor" game, the "Assessor" chooses the "hawk" strategy if they have a greater "resource holding potential" (RHP -- this can be for example fighting ability), and chooses the "dove" strategy if their RHP is less than that of their opponent.

Excellent lecture notes on sequential assessment can be found at the web site by Barry Sinervo of UC Santa Cruz, and at the web site of Gerald Wilkinson at the University of Maryland.