How Do You Use the Matrix in Game Theory?


Martha Robinson

Game theory is a mathematical approach to understanding decision-making that has become increasingly popular in fields such as economics, political science, and psychology. One of the most important tools in game theory is the matrix, which is used to represent situations where two or more players must make decisions that will affect each other’s outcomes. In this article, we’ll explore how the matrix is used in game theory and provide some examples to help illustrate its importance.

What is a Matrix?

A matrix is simply a table that represents the different possible outcomes of a given situation. In game theory, these outcomes are often referred to as “payoffs,” and they represent the rewards or penalties that each player receives based on their actions and the actions of their opponents.

The matrix itself consists of rows and columns, with each row representing one player’s choices and each column representing another player’s choices. The cells in the matrix contain the payoffs for each possible combination of choices.

Example: The Prisoner’s Dilemma

One classic example of how the matrix is used in game theory is the Prisoner’s Dilemma. In this scenario, two suspects are arrested for a crime but are held separately and cannot communicate with each other. Each suspect must decide whether to cooperate with the police (by confessing) or stay silent (by remaining silent).

If both suspects remain silent, they both receive a relatively light sentence (let’s say 1 year in prison). However, if one suspect confesses while the other remains silent, the one who confesses receives a reduced sentence (let’s say 6 months) while the other receives a harsher sentence (let’s say 10 years). And if both suspects confess, they both receive a moderately harsh sentence (let’s say 5 years).

To represent this scenario using a matrix, we would create a table like this:

Remain Silent Confess
Remain Silent (1 year, 1 year) (10 years, 6 months)
Confess (6 months, 10 years) (5 years, 5 years)

The rows and columns represent the choices of the two suspects: remain silent or confess. The cells contain the payoffs for each possible combination of choices.

Using the Matrix to Analyze Strategies

Once we have a matrix representing a particular scenario, we can use it to analyze different strategies that each player might employ. One common approach is to look for “dominant strategies,” which are actions that a player should always take regardless of what their opponent does.

In the Prisoner’s Dilemma example above, each player’s dominant strategy is to confess. This is because if one player remains silent while the other confesses, the confessor gets off with a lighter sentence. And if both players confess, they both receive a moderate sentence.

However, even though both players have dominant strategies of confessing, this does not lead to an optimal outcome for either player. In fact, both players would be better off if they could somehow coordinate to remain silent (which would result in both receiving light sentences). This is an example of a “prisoner’s dilemma” because even though cooperation would be in both players’ best interests, neither has any incentive to cooperate unless they can be sure their opponent will cooperate as well.


The matrix is an essential tool in game theory, allowing us to represent complex decision-making scenarios and analyze the strategies that different players might employ. By highlighting dominant strategies and identifying situations where cooperation could lead to better outcomes for all players, the matrix helps us understand how games are played and how we can make better decisions in a wide variety of contexts.