Gamasutra is running an article written by Tim Hong of EmSense in which he describes the research his company did into the physiological reactions various games engender in players. In addition to outward cues like breathing and movement, EmSense also scans brainwaves and heart activity to provide a more complete picture of how a gamer is responding to what he sees and does. They collected hundreds of hours worth of data and made comparisons among a variety of shooters, such as Gears of War 2, F.E.A.R, and Half-Life 2. They found some interesting information on how pacing, tutorials, and cutscenes can affect a player's level of engagement with the games.