There's an optimal strategy for winning multiple rounds of rock, paper, scissors: be as random and unpredictable as possible. Don't pay attention to what happened in the last round.

However, that's easier said than done.

To find out how brains make decisions in a competitive setting, we asked people to play 15,000 games of rock, paper, scissors while recording their brain activity.

Our results, now published in Social Cognitive and Affective Neuroscience, found that those who were influenced by previous rounds really did tend to lose more often.

We also showed that people struggle to be truly random, and we can discern various biases and behaviors from their brain activity when they make decisions during a competition.