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Trigger strategy

Trigger strategy is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Trigger strategy rather than just read about it. In short: In game theory, a trigger strategy is any of a class of strategies employed in a repeated non-cooperative game. A player using a trigger strategy initially cooperates but punishes the opponent if a certain level of defection (i.e., the trigger) is observed.

Key takeaways

  • Trigger strategy belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Trigger strategy to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Trigger strategy from memory before moving on to harder problems.

Reference excerpt

In game theory, a trigger strategy is any of a class of strategies employed in a repeated non-cooperative game. A player using a trigger strategy initially cooperates but punishes the opponent if a certain level of defection (i.e., the trigger) is observed. The level of punishment and the sensitivity of the trigger vary with different trigger strategies.

Trigger strategies Grim trigger (the punishment continues indefinitely after the other player defects just once) Tit for tat (the punishment continues as long as the other player defects) Tit for two tats (a more forgiving variant of tit for tat)

References Textbooks and general reference texts Vives, X. (1999) Oligopoly pricing, MIT Press, Cambridge MA (readable; suitable for advanced undergraduates.) Tirole, J. (1988) The Theory of Industrial Organization, MIT Press, Cambridge MA (An organized introduction to industrial organization) Classical paper on this subject Friedman, J. (1971). A non-cooperative equilibrium for supergames, Review of Economic Studies 38, 1–12. (The first formal proof of the Folk theorem (game theory)).

Worked examples

Example 1 — a first encounter with Trigger strategy

Start with the simplest possible case. Write down what Trigger strategy claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Trigger strategy before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Trigger strategy ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Trigger strategy

In research
Trigger strategy appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Trigger strategy in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Trigger strategy is common in secondary-school and first-year university syllabi. It links to neighbouring topics Economic theories stubs, Microeconomics stubs, Non-cooperative games, so understanding it makes those chapters shorter.
In everyday life
Look for Trigger strategy outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Trigger strategy in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Trigger strategy means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Trigger strategy out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Trigger strategy in simple terms?

In game theory, a trigger strategy is any of a class of strategies employed in a repeated non-cooperative game. A player using a trigger strategy initially cooperates but punishes the opponent if a certain level of defection (i.e., the trigger) is observed.

Why does Trigger strategy matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Trigger strategy?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Trigger strategy.

Tags

  • Economic theories stubs
  • Microeconomics stubs
  • Non-cooperative games

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