Lecture 18
 - Imperfect Information: Information Sets and Sub-Game Perfection

Lecture 18 - Imperfect Information: Information Sets and Sub-Game Perfection

Author: William Sheppard June 8, 2018 Duration: 1:15:57
We consider games that have both simultaneous and sequential components, combining ideas from before and after the midterm. We represent what a player does not know within a game using an information set: a collection of nodes among which the player cannot distinguish. This lets us define games of imperfect information; and also lets us formally define subgames. We then extend our definition of a strategy to imperfect information games, and use this to construct the normal form (the payoff matrix) of such games. A key idea here is that it is information, not time per se, that matters. We show that not all Nash equilibria of such games are equally plausible: some are inconsistent with backward induction; some involve non-Nash behavior in some (unreached) subgames. To deal with this, we introduce a more refined equilibrium notion, called sub-game perfection.

Ever wondered how the strategies behind a high-stakes poker game, a political campaign, and a corporate merger might actually be connected? Yale Open Courses ECON 159: Game Theory, presented by William Sheppard, pulls back the curtain on the fascinating science of strategic decision-making. This isn't just an academic lecture series; it's a deep dive into the frameworks that explain how we interact when our choices directly impact others. Each episode unpacks core concepts-from Nash equilibrium and backward induction to credibility and signaling-using clear explanations that make these powerful ideas accessible. You’ll hear these theories brought to life through engaging examples that stretch far beyond textbook economics. Discussions might pivot from classic parlor games to analysis drawn from film narratives, historical events, and current political dilemmas, showing just how pervasive strategic thinking is in our world. The content is drawn directly from the renowned Yale College course, capturing the dynamic atmosphere of a campus classroom. For anyone curious about the hidden rules of competition and cooperation in everyday life, this podcast serves as a compelling guide. Tune in to train your mind to see the strategic layers in everything from simple interactions to complex global systems.
Author: Language: English Episodes: 24

Yale Open Courses ECON 159: Game Theory
Podcast Episodes
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At the start of the lecture, we introduce the “formal ingredients” of a game: the players, their strategies and their payoffs. Then we return to the main lessons from last time: not playing a dominated strategy; and putt…
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We introduce Game Theory by playing a game. We organize the game into players, their strategies, and their goals or payoffs; and we learn that we should decide what our goals are before we make choices. With some plausib…