Buried within slashdot comments on an article about a brain-computer interface was a suggestion to user dasher for input since the input is "simply up and down." Up and down is all well and good, but since dasher's speed advantage is based on analog input, and brain readers being not-so-good at that, it would take a while to iterate through all the options. Dasher-style prediction seems fine by me, but at that point the user should be focusing on choosing between letters instead of thinking "up" or "down." My criticisms are not with dasher, but with the way the commenter presented its use in this application. I think it'd work well with an eyetracker, but that's not a computer-brain interface.
Anyway, the up-side to all of this is that I was introduced to dasher at all, and wanted to try and get it to work on my laptop. It only has a beta version for OS X, but I decided to be adventurous.
I learned when they say beta, they really mean it. Dasher crashed possibly a dozen times before I got it to work long enough in order to actually see how it felt. And the feelings were only lukewarm. Maybe not even that. Maybe more like the temperature of a shirt left on the floor at night...that you have to put on in the morning right after you get out of your really warm bed.
Dasher uses a grid input you control with a mouse, stylus, etc. Right is "continue with this selection", left is "go back", and the magnitude indicates how fast. Up and down are used for selection of letters, some being enlarged predictively for easier selection. The left/right portion of the grid is excellent and works in a helpful way to select letters. The up/down is a disaster.
The predictive enlargement tends to crowd out letters that one might actually want. Not every time I select a t do I want it to be followed by an h and an e. Sorry, dasher, tis true. The main problem, however, is the very nature of our alphabet. The standard ABCD... is really totally arbitrary. I know librarians who still mutter the grade school songs when sorting books. It just isn't intutive. We don't think "now I want an l, which is between k and m." There is no really good way to sort our letters. I think that the problem of alphabetical organization is an interesting one worth pursuing further. I need to hunt down a linguist.
Personally, I think in terms of phonemes, which translate into letters based on experiential knowledge. If dasher stopped trying to be a glorified keyboard input it might actually get somewhere. But so long as there is a button that gives me an a, why on earth would I ever use a mouse? I mean, really.