Game theory studies what happens when your best choice depends on what someone else does.
That makes it different from a normal optimization problem. You are not just choosing against nature. You are choosing against another decision-maker.
This is why game theory is useful for economics, politics, biology, climate policy, business, and everyday social situations.
A Simple Game
Imagine two companies deciding whether to be honest about sustainability claims or exaggerate them.
If both are honest, customers can trust the market.
If one exaggerates while the other stays honest, the exaggerating company may get more attention.
If both exaggerate, trust collapses and everyone looks suspicious.
The problem is not that every player is evil. The problem is that the incentives may reward behavior that damages the whole system.
Payoffs
A payoff is the result a player gets from a choice.
Payoffs do not have to be money. They can represent reputation, time, risk, social status, votes, or survival.
In a classroom, students can create payoff tables to see how a system pushes people toward certain choices.
Dominant Strategy
A dominant strategy is a choice that is best no matter what the other player does.
If exaggerating gives a company more attention whether the other company is honest or not, exaggeration may become dominant.
That is dangerous, because individually rational choices can produce a collectively bad result.
Nash Equilibrium
A Nash equilibrium happens when no player wants to change their choice alone.
It does not mean the outcome is good. It only means the system is stable.
That distinction is one of the most important ideas in game theory.
Sometimes a bad outcome survives because no single player has an incentive to move first.
COSMO Discussion Prompt
Ask students:
Can you think of a situation where everyone would be better off cooperating, but each individual has a reason not to?
Possible examples:
- group projects,
- traffic,
- studying for a curved test,
- pollution,
- social media attention,
- pricing competitions.
Then have them build a payoff table.
Takeaway
Game theory helps students understand that behavior is shaped by systems.
When incentives are misaligned, telling people to “do better” may not be enough. The better question is: how do we change the game?