QWERTY vs DSK: An Ergonomic Analysis Jim Blair: >> But (as I have claimed before), to evaluate a situation >> you need to look at the basics and not just the results of >> "studies". And looking at the keyboards and the English >> language letter frequency tables, it looks to me like >> the DSK pattern of keys is clearly "better" for modern >> keyboards which don't jam if typed "too fast". Grinch: >What the heck does all this mean? That you think you can identify the >typing speed of a keyboard just by looking at it? That you disregard >empirical data from studies.... Hi, My initial reaction was that I could not estimate the typing speed of a keyboard from inspection, because different people will have different skill levels, which will result in different finger motion speeds. But then I realized that the issue is not the absolute speed, but the relative speed of people with the same skill level on the two different keyboard patterns. This can be estimated, based on certain assumptions. I have calculated what I call the "theoritical relative typing speed" of the QWERTY (Scholes) and DSK (Dvorak) keyboards, based on the assumption that the time to type an English language text is proportional to the distance the typists fingers must move during the process. From the English language letter frequency chart at: http://www.trincoll.edu/depts/cpsc/cryptography/caesar.html and the DSK keyboard at: http://www.mwbrooks.com/dvorak/ and my measurments of the distance between keys, and (d)the distance needed to depress the key to cause the letter to register, I created a spreadsheet to calculate the the relative distances (times) for a given value of d. It is at: http://www.geocities.com/capitolhill/4834/qwerty.xls The assumption is that the fingers rest in the top of the home keys asdf (left hand) and jkl; (right hand) for the QWERTY keyboard; but aoeu (left hand) and htns (right hand) for the DSK keyboard. To type any of these keys, the distance moved is d. All other letters require moving the closest finger a distance of about 20 mm (except for the letters y and b on the QWERTY; x and f on DSK: they require moving the closest finger 30 mm) plus the depression distance d. These letter weights are in columns C and F of the spreadsheet. Consider a typical 1000 keystroke sequence (about 200 words). The distance of finger movement for each letter is its frequency of appearing (column B) times the distance of finger movement it requires. These are columns D and G of the spreadsheet. The ratio of the sums of the distances are tabluated for several values of d. Puncituation marks were not considered: they would give a very slight advantage to QWERTY since the ; is under the right little finger on that keyboad, while all other puncituation marks are a 20 mm reach on either keyboard. I have seen no other attempt to predict the relative typing speed of different keyboard patterns, but I would expect that August Dvorak would have made an effort to do this. Comments: For an "ideal typewriter" (one where d =0) the DSK advantage would be a maximum of about 60% faster. This would be a keyboard where the key would print when touched. For my Hewlett Packard, the keys need to be depressed by about 3 mm to print. This should give the DSK an edge of about 47%. An old IBS Selectric at our lab has a d = 5 mm, which should cut the DSK advantage to about 40% Mechanical twpewriters required a larger d and so provided the DSK with a smaller advantage, perhaps to as little as 20%. The results of the DSK advantage are listed below as a function of p. p (mm) QWERTY/DSK times 0 1.60 "Ideal" typewriter 3 1.47 my HP kewboard 5 1.40 IBM Selectric 10 1.31 mechanical ? 20 1.20 very old mechanical And finally, Robert Vienneau claims that this issue is not about egronomics but about politics. "Liberals" and statists like the idea of "lock in" and path dependence while "Conservatives" and "Libertarians" doubt it. (or did I mis-read him??) But I am on the "right/libertarian" side of the political spectrum (so they tell me: I see myself as "in the center", as of course I am relative to---me!). But I think there is at least something to the idea of 'lock in', and that History does matter. ,,,,,,, _______________ooo___(_O O_)___ooo_______________ (_) jim blair (jeblair@facstaff.wisc.edu) Madison Wisconsin USA. This message was brought to you using biodegradable binary bits, and 100% recycled bandwidth. REPLIES: cpw@rahul.net > However, I'm responding to this thread because I have to question > your methodology in just looking at distance the fingers move. As I said > in that other thread, I'm a pretty fair touch typist on QWERTY, yet I have > problems because I'll mistype certain key combinations, 'more' comes out > as 'moer' or 'mroe'. > One thing about the QWERTY that is ergonomic, even today, > is that it forces you to alternate hands a lot on different letters (I > got that from the URLs Grinch led me to). This is something that a test > merely of distance to keys wouldn't catch. I agree that distance is not the entire story, and view my analysis as a "first approximation" to which refinements can be added. But surely the distance of finger movement must play a role in both the time, and the extent of fatigue in typing. And on the alternating hands, I would expect DSK to have the edge here. Note that the DSK keyboard has the vowels under the left fingers, and the most used consonants under the right fingers. Your problem word "more" has the common alternating consonant-vowel pattern that DSK was designed to deal with. You would have to use the same hand twice in succession to make either of those errors in DSK. But on a QWERTY board you need to use the right hand twice and then the left twice to make the word "more" come out right. That "mroe" is the result of trying to alternate hands. kenfran wrote: > This does not allow for differences caused by > letter combinations where the same finger has > to type successive letters, such as the words > "jump" and "junk", where the finger has to > travel from the U key to the M or N key, > thus needing more movement than if seperate > fingers were used. An analysis of common > letter combinations would be needed for this. Hi, Notice that in your examples, while the QWERTY keyboard has all of the letters in "jump" and "junk" use the right hand only, (and 3 of the 4 use the same right index finger), with a DSK keyboard, the hand sequence is left, left, right, left. Not great alternation of hands but better than QWERTY. It is almost as if the QWERTY keyboard were designed to make those words hard to type fast :-0 -- ,,,,,,, _______________ooo___(_O O_)___ooo_______________ (_) AND: jim blair wrote: I agree that distance is not the entire story, and view my analysis as a "first approximation" to which refinements can be added. But surely the distance of finger movement must play a role in both the time, and the extent of fatigue in typing. C Post wrote: > Consider also that the QWERTY keyboard was designed for manual typing, > in which the fingers must supply enough mechanical energy to actuate the > mechanism and strike the type against the platen hard enough to form the > characters. The kinesiology of electronic keyboard operation is totally > different. > > -- royl@not.this.partistar.ca Hi, I thought about this when I did my analysis. I wish I had some old mechanical typwriters to examine and measure. But the effect of pushing the key harder should be the equivalent of moving the finger a greater distance, both in terms of time and of fatigue. This would make the "effective d" greater than the measured movement, which would reduce the DSK advantage. Perhaps even enough to reduce it below what could be easily measured in a study, especially a study using people who already knew how to type in QWERTY, and would have an "unlearning curve" before they could start a new "learning curve". But in a study of "virgins" using modern electronic keyboards, an advantage of over 40% should be measurable. AND: jim blair: .... But the effect of pushing the key harder should be the equivalent of moving the finger a greater distance, both in terms of time and of fatigue. C Post wrote: > .... I can remember using a manual typewriter, and the finger > action is quite different. You can sometimes see scenes of typists in > old movies, and their hands really jump up and down a lot compared to > electronic typists' hands. > > -- royl@not.this.partistar.ca Hi, Yes, but any "extra" motion of the hands has the effect of reducing the advantage of the DSK key pattern relative to the QWERTY pattern. The "shorter distance" to the key becomes less important as the total distance moved becomes greater. The analysis of hand motion in a film or video of mechanical and electronic typists would provide a better estimate of the relative merits of the 2 keyboard patterns. And the effect you describe ("bouncing on the keys" to get the momentum to push them down) could reduce the DSK advantage below the level that could be measured in a mechanical twpewriter. This could explain a lot of the studies that found little to no difference between the two keyboards. -- ,,,,,,, _______________ooo___(_O O_)___ooo_______________ (_) jim blair (jeblair@facstaff.wisc.edu) For a good time call http://www.geocities.com/capitolhill/4834 For an improved analysis, see: http://www.visi.com/~pmk/evolved.html