By Daniel Cossins IN THE film A Beautiful Mind, John Nash and his buddies, all of them graduate students in mathematics at Princeton University, are sitting in a smoky bar when a group of women walk in. As the men tease each other about their chances, Nash is struck with inspiration. Is there a logical, mathematical way of working out the best strategy for each man getting a date? Next thing you know he’s shambling out of the bar, and spends the night furiously scribbling unfathomable-looking equations. It sounds a little crass, and the episode probably never happened in reality. But in a ham-fisted, Hollywood sort of way, it does hint at how game theory, the branch of mathematics Nash helped to make famous, can apply to our everyday lives. In fact, we use it all the time without even realising. “Every time you think about what you should do in terms of what someone else will do in response, you’re doing rudimentary game theory,” says Kevin Zollman of Carnegie Mellon University in Pittsburgh, Pennsylvania. The trouble is, we are novices. When we need to think through situations several steps ahead or when they involve more than just a few people, we start to make mistakes. But delve into the theory just a little – there’s no need to be a maths whizz – and you can harness some of the insights to make smarter moves in your own life. Lesson one is that there are different sorts of games. Broadly speaking, there are zero-sum games, in which one player gains what the other loses, and variable-sum games,