The study, published Wednesday by British researchers, used functional MRI brain scans to examine people while they played a computerized game for a modest monetary reward. Nineteen subjects played the games in which they had to catch a 'high-payoff prey' or 'low-payoff prey.' They performed worse when trying to catch the high-payoff prey. Brain scans showed increased activity in the ventral mid-brain, an area linked to motivation and reward response. '(H)ighly skilled players sometimes perform catastrophically when on the brink of victory,' the authors wrote. 'Often called `choking under pressure,' this phenomenon extends beyond sport.' Examples include students taking academic tests and tasks that are performed in front of an audience. This study suggests that it's the presence of an incentive or reward that causes people to choke and that they might perform better if they didn't care as much. The intense desire to perform well causes an excessive arousal and activity in the brain that could interfere with decision-making, memory and attention. The researchers note, however, that many variables are linked to choking under pressure. Anxiety, for example, can impair performance. But the fact that subjects in this study performed worse on a computer game in which the reward was relatively modest suggests that being over-motivated can be a stumbling block. 