text:  Yeah. Did you perform worse than you expected, given what you could do? To me, that's a choke. This is the president of Dartmouth College. My name is Sian Bylock. Sian is also a cognitive scientist who spent most of her career studying what happens in our brains when we crack under pressure. For Sian, there was one particular day in high school when this happened to her, and she will never forget it.