Researchers at the University of Manchester and Oxford University have discovered that players of games of sufficient complexity – like chess and poker – do not always, or even often, make rational decisions, because it’s simply too difficult for their brains to measure all of the available options:

Much of traditional game theory, the basis for strategic decision-making, is based on the equilibrium point — players or workers having a deep and perfect knowledge of what they are doing and of what their opponents are doing.

Dr Galla, from the School of Physics and Astronomy, said: “Equilibrium is not always the right thing you should look for in a game.”

“In many situations, people do not play equilibrium strategies, instead what they do can look like random or chaotic for a variety of reasons, so it is not always appropriate to base predictions on the equilibrium model.”

The number of players of a game also influences whether or not people make rational decisions; the researchers suggest that the more players in a game, the less rationally players act. This may explain why you have a harder time making the right decision in a 16-player game of Halo on a huge map than in a four player game on a small one.