Why I won't be saving the world

There I was, sitting in my first-year University kitchen. It was the social hub, really; we lacked any shared space except the kitchen. A girl from an American university, staying for a semester, was sat with me.

“Stephen,” she said, for that is my name, “you’re pretty smart.”
I hate it when people say that to me. It doesn’t happen regularly or anything, but it has happened in the past. How are you supposed to respond to such a flattering accusation?