In Left 4 Dead, test subjects had their sweat monitored, with values assigned to how much they were responding to the action.

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But perhaps its beautiful backlit keyboard, spacious Synaptics Clickpad and the sheer satisfaction of shooting Left 4 Dead zombies will help soothe the financial pain.

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What I imagine would be much better than trying to blast your way through Left 4 Dead on the PS Vita would be playing the game with a pair of Google Glasses.

FORBES: Playing Left 4 Dead On Sony's PlayStation Vita

Mike Ambinder is the company's very own experimental psychologist and he's been outlining some of Valve's work with biofeedback technology, including eye-motion controls for Portal 2 and perspiration-based gaming adjustments on Left 4 Dead.

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Oct 2, 2012 -- Valve, creators of best-selling game franchises (such as Counter-Strike, Half-Life, Left 4 Dead, Portal, and Team Fortress) and leading technologies (such as Steam and Source), today announced the first Software titles have launched via Steam, marking a major expansion to the platform known as a leading destination for PC and Mac games.

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