We compare the performance of high-ability adolescent girls and boys who participated in a long-running Korean television quiz show. There is a significant gender gap in performance – in favour of boys – when we pool all round 1 episodes of the quiz show. To investigate underlying mechanisms that might explain this, we explore how performance varies under different exogenously-varied rules of the game. We find that there are no gender gaps in performance when stress is kept to a minimum – that is, in games without fastest-finger buzzer, knock-outs or penalties. However, in games with some of these features, there are significant gender gaps. In addition, we examine performance in round 2 of the shows, where we find larger gender gaps. Finally, we use question-by-question panel data to track performance in games where players stay in for 25 questions. Here we find that girls are less likely to respond faster especially when their winning probability is higher. Further, the gender gap is more salient at the end of the game. The results are consistent with gendered behavioural responses to psychological pressure.