We compare the performance of high-ability adolescent girls and boys who participated in a a long-running Korean television quiz show. We find there is a gender gap in performance - in favour of boys - across episodes of the quiz show. To investigate underlying mechanisms that might explain this, we explore how male and female performance varies under different rules of the game. We find that there are no gender gaps when stress is kept to a minimum - that is, in games without fastest-finger buzzer, knock-outs or penalties. However, in games with these features, there are significant gender gaps. In addition, we examine performance in Round 2 of the shows, where we find larger gender gaps. These are consistent with girls being increasingly hindered by psychological stress and risk aversion as competition is higher. Finally, we use panel data to estimate performance in the games in which 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 also consistent with gendered behavioural responses to psychological pressure.