As I have improved my typing skills over the years, I have noticed that I increasingly make errors at the whole word level rather than at the wrong-letter or transposed-letter stage. For example, when I try to type the word “universe” I frequently find that I have typed the word “university” before I realise that I have made an error. “University” is a word that I type many times a day; “universe”, perhaps once a week or less. This would seem to relate to the idea of “chunking” in memory —instead of controlling each individual letter being typed, instead I am chunking together the typing activity of whole words as “basic units”. There is an argument (from Rumelhart and McClelland, Parallel Distributed Processing) that when experienced typists type a word like vacuum, where the first three letters are all in the left hand, the right hand is moving towards the letter ‘u’ before the left hand has finished the “vac” part of the word.
Another piece of evidence for this: a colleague of mine has said in an email: “slip of the fingers: Venue for the meeting will be S122A, (*not* S110B)”. Fingers would have to slip very precisely to type the exact sequence of letters required to type the name of one room rather than another; the slip is at a much earlier stage in the cognitive process! It would be interesting to do a proper study of this kind of mistyping, perhaps this would make a good student project.