I have a strong interest in learning how people's uses of technologies changes the way they think– or less grandly, how it shapes the way they perform cognitive tasks or approach problems. Recently, I found an example of something I do that's definitely an artifact of my long engagement with a very specific technology: I realized I spell with my hands.
The other night, my wife and I were at the dining room table, each of us working on stuff. (Since she's a teacher at a pretty demanding school, she often has papers to grade in the evening.) She asked me how to spell a long word. I thought about it for a second, and couldn't just recite the letters, even though I was sure I knew how it was spelled. So I typed it.
Of course, I can recite the spelling of plenty of words, but after thirty years of typing, complex spelling is something I do with my hands more than my mind's eye. I know a word is misspelled when I feel my fingers hit the wrong keys, or reverse the order of a pattern. For me, correct spelling is a matter of feeling my fingers move over the keyboard in the right, comfortable way, not a matter of thinking "this word is spelled like this," then translating that into a set of motions. The keyboard has become an interface between the words I know how to spell, and the actual act of spelling them correctly.
This helps explain why I find using the predictive text feature on cell phones a somewhat puzzling experience. On a keypad with predictive text turned on, you really do have to think about the spelling of a word, because you're essentially feeding the phone clues about the word you want it to spell. Hit the wrong number on the keypad, and it's led astray, a sure as giving someone the wrong clue in a mystery will lead them to a mistaken conclusion. What makes it more confusing is that as you hit the keys, the phone may guess a completely different word than it had before; and of course, some keypad combinations can spell several different, equally popular words (46 can be "in" or "go," or a bit less likely, "ho").
For someone accustomed to spelling on a QWERTY keyboard, this is a pretty mystifying interaction. Of course, I'm getting better at it; but writing on a traditional keyboard and a keypad aren't merely different activities in terms of the fingers you use, or the prominence of the thumb versus the other digits; it places different cognitive demands on someone who's grown up spelling with his hands.