Heart rate, temperature, respiration, and perspiration: These are our autonomous functions–our core physiological processes–that signal stress or arousal and can betray our otherwise cool exteriors. Stanford researcher Gregory Kovacs is reading these signals through a modified Xbox game controller. By adding a new, sensor-laden back plate, he can measure heart rate, blood flow, rate and depth of breath, and how hard and fast the user shakes the controller. In response to these measurements, Kovacs has designed a game that can maximize excitement by adding more stimulus (like bad guys or explosions) whenever a gamer’s heart rate drops. Or it could do the reverse, ramping down the zombie factor for someone who wants to take it easy (but insists on playing zombie games to do so).