Economic Classroom Experiments/Rock, Paper, Scissors

Introduction to a simple hand game that is often used for 'random' decision-making, in much the same manner as drawing straws. However, under the right circumstances, it can be a game of skill.

Level
Any level

Prerequisite knowledge
None

Suitable modules
Any

Intended learning outcomes

 * 1) Understanding of how the game is played
 * 2) Understanding of how the intended randomness of the game can be undermined by skilled play

Abstract
Students (in pairs) both present a hand shape at the same time. There are shapes representing rock, scissors and paper. The student presenting the 'better' hand wins (or there is a draw). On a simple examination, it would seem that each hand shape is equally likely to win. However, over a series of games, psychological effects come into play, and a skilled player can skew results in their favour.

Discussion of Likely Results
In a simplistic analysis, each of the three hand shapes offers an equal chance of winning (an analysis borne out when the game is played against a computer). However, human players will unintentionally exhibit patterns of behaviour, that a skilled player can observe over a long series of games. The skilled player can then use those patterns to improve their own plays.

Of course, skilled players will deliberately alter their playing patterns to foil such pattern observation. But even these countermeasures are inevitably imperfect, and in the long run, the more skilled player will win more games.

From this, one can demonstrate that even seemingly even-handed games can be skewed by an observant player.