Teris

I have been working on Brain-computer Interface (BCI) for a while. I don't know much about the algorithm used by Emotiv EPOC. But most of the BCI nowadays use the change in brain signal during motor imagery (like imagining moving your hand, instead of actually moving it. Not visual imagination, but imagining subjectively moving your hand. Yes, that a bit hard to explain...) for control. During motor imagery, there is a decrease in energy of the brain signal in certain frequency band, so the computer can analyze this signal feature and classify your intention. And different motor imagery (like moving hand, moving legs etc.) will have different spatial distribution over your head and so can be used to differentiate against different kinds of intention.

Usually it is the motor imagery that is important. Saying "right" out loud in the heart can't create a clear signal for the device to work on, simply because verbal intention won't produce noticeable change in brain signal. Of course, over time the brain will adapt and you can stop imagining the hand movement and think directly at the intended action. But it is always better to start with motor intention first.

BCI is really as much about the subject as the device. That said, I am still doubtful whether such a small device can do the job well. In research we usually use brain signal amplifier that costs more than $10,000.