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.

Overview

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.