Earlier quoted context omitted.
I'm not being clear, I don't think that thinking the words "left left up up" would be detectable through EEG. When I say detecting movement, I mean things like imagining moving a hand, a foot or a tongue. These movements use distinct areas of the brain so you can distinguish between them by looking at where on the scalp the change occurred. This is done in ways that are known to be close to perfect. However, you prob…
Would it (now, or in the reasonably realistic future) be able to detect me imagining my fingers typing "call mom" on a keyboard?
So you couldn't distinguish individual fingers with todays technology. If it was ever to be done, I'd expect that it would be done with the same algorithms as we use today, but with much denser electrodes. If I were to bet, I'd bet that this would be physically impossible, but I'm not as confident as I am with saying we wont be able to detect who I want to call.
[1] http://en.wikipedia.org/wiki/File:Human_motor_cortex_topogra...