Valve Co-founder Gabe Newell wants to do a scientific study on gamer's brains while they're playing so they can design and develop games even better. He published an extensive article about why and how he's so interested in making it happen.
Valve is the company that brought us such fun things as The Orange Box, Left 4 Dead, and the Counter Strike series.
In that article, Newell said, among many other things:
We can know for sure of something is actually frightening the player - their heart rate is going up, their respiration stats are peaking, appropriate parts of their brains are being activated. Direct measurement of players’ arousal states and responses to the things we’re doing is super exciting. It just will allow us to be much more analytical about the decisions that we’re making and the roller coaster ride we’re trying to create for the player.