Developers have been trying to incorporate biofeedback into gaming for years. In 1984, Atari experimented with a headband called MindLink, which used electromyographic (EMG) sensors to detect muscle movements, allowing players to move an on-screen cursor with a frown or a raised eyebrow. In 1998, AmTex developed a game called Bio Tetris for the Nintendo 64. A heart-rate sensor clipped to the player's ear lobe allowed players to slow the speed at which the Tetris blocks fell by remaining calm. Neither took off. So what's different this time? One factor is the dazzling success of Nintendo's Wii - 20 million consoles sold and rising. It dispenses with the traditional joystick and instead uses gestures to control the game via a hand-held wireless motion sensor. Its success has made it clear that people are ready for new ways to interact with games. Another factor is that the core technology is different, though whether it works is another matter. On the surface the claims seem plausible. Neurologists have long known how to read emotional states off an EEG, and Mindball apparently picks up alpha waves - a hallmark of mental calmness. But there are also many reasons to be sceptical. Where neurologists use as many as 120 EEG sensors all over the scalp, gaming headsets have just a handful - or, in NeuroSky's case, just one. The headsets don't use the sticky conductive gel that medical EEGs need to transmit the signal from the scalp to the electrode. On top of that, EEGs are notoriously "noisy" - prone to interference from nearby electrical devices as well as the electrical activity produced by muscles, especially the heart. Even blinking can play havoc with an EEG signal. So how do they do it? Although the firms are cagey about how exactly their technologies work, there are a few details to go on. The number of electrodes seems to come down to a question of resolution. Medical and research-grade EEGs need to be sensitive enough to detect subtle signals amid a chorus of electrical brain activity. For gaming, the chorus itself is sufficient. "We can't achieve the same resolution as medical EEGs, but it's enough to detect the basic brainwaves," Yang says. Dealing with interference is another matter and perhaps the fledgling industry's biggest challenge. EMG signals, produced by muscle activity, are a particular problem because they can be an order of magnitude bigger than those produced by the brain. Yang agrees that this is a challenge, but says the trick is to develop software that can recognise and filter out unwanted signals. "Our core technology is filtering," he says. In any case, it may not be necessary to filter out all EMG signals, says Tan. Some could be turned to the developers' advantage, as there is a strong correspondence between involuntary facial muscle contractions and your cognitive states and emotions, he says. So EMG signals can be used to supplement the EEG. In fact, the companies already use other bio-information from ECGs and GSR. Heart rate and sweating are both good measures of how physically and mentally aroused someone is. The trick is to combine all the measurements to get an overall sense of the player's mental and physical state. "Each of these sensors gives us a little piece of the picture," Tan says. Using slight variations of this approach NeuroSky and its competitors claim to have cracked it. Continue reading here