Chicken

The game of chicken, also known as the hawk–dove game or snowdrift game, is a model of conflict for two players in game theory.

The principle of the game is that while the outcome is ideal for one player to yield (to avoid the worst outcome if neither yields), but the individuals try to avoid it out of pride for not wanting to look like a ‘chicken’. So each player taunts the other to increase the risk of shame in yielding.

However, when one player yields, the conflict is avoided, and the game is for the most part over.

The name “chicken” has its origins in a game in which two drivers drive towards each other on a collision course: one must swerve, or both may die in the crash, but if one driver swerves and the other does not, the one who swerved will be called a “chicken”, meaning a coward; this terminology is most prevalent in political science and economics.

The name “hawk–dove” refers to a situation in which there is a competition for a shared resource and the contestants can choose either conciliation or conflict; this terminology is most commonly used in biology and evolutionary game theory.

From a game-theoretic point of view, “chicken” and “hawk–dove” are identical; the different names stem from parallel development of the basic principles in different research areas. The game has also been used to describe the mutual assured destruction of nuclear warfare.

Game theoretic applications

Both Chicken and Hawk–Dove are anti-coordination games, in which it is mutually beneficial for the players to play different strategies. In this way, it can be thought of as the opposite of a coordination game, where playing the same strategy Pareto dominates playing different strategies.

The underlying concept is that players use a shared resource. In coordination games, sharing the resource creates a benefit for all: the resource is non-rivalrous, and the shared usage creates positive externalities. In anti-coordination games the resource is rivalrous but non-excludable and sharing comes at a cost (or negative externality).

Because the loss of swerving is so trivial compared to the crash that occurs if nobody swerves, the reasonable strategy would seem to be to swerve before a crash is likely. Yet, knowing this, if one believes one’s opponent to be reasonable, one may well decide not to swerve at all, in the belief that they will be reasonable and decide to swerve, leaving the other player the winner.

This unstable situation can be formalized by saying there is more than one Nash equilibrium, which is a pair of strategies for which neither player gains by changing their own strategy while the other stays the same. (In this case, the pure strategy equilibria are the two situations wherein one player swerves while the other does not.)

Pre-commitment

One tactic in the game is for one party to signal their intentions convincingly before the game begins.

For example, if one party were to ostentatiously disable their steering wheel just before the match, the other party would be compelled to swerve.

This shows that, in some circumstances, reducing one’s own options can be a good strategy. One real-world example is a protester who handcuffs themselves to an object, so that no threat can be made which would compel them to move (since they cannot move).

Another example, taken from fiction, is found in Stanley Kubrick’s Dr. Strangelove. In that film, the Russians sought to deter American attack by building a “doomsday machine”, a device that would trigger world annihilation if Russia was hit by nuclear weapons or if any attempt were made to disarm it.

However, the Russians had planned to signal the deployment of the machine a few days after having set it up, which, because of an unfortunate course of events, turned out to be too late.

Players may also make non-binding threats to not swerve. Such threats work, but must be wastefully costly if the threat is one of two possible signals (“I will not swerve”/”I will swerve”), or they will be costless if there are three or more signals (in which case the signals will function as a game of “Rock, Paper, Scissors”).