Captain's Log

These ergonomic studies are particularly interesting because the claimed advantage of the Dvorak keyboard has been based historically on the claimed ergonomic advantages in reduced finger movement. Norman and Rummelhart's discussion offers clues to why Dvorak does not provide as much of an advantage as its proponents have claimed. They argue, For optimal typing speed. keyboards should be designed so that:

A. The loads on the right and left hands are equalized.
B. The load on the home (middle) row is maximized.
C. The frequency of alternating hand sequences is maximized and the frequency of same-finger typing is minimized.

The Dvorak keyboard does a good job on these variables, especially A and B: 67% of the typing is done on the home row and the left-right hand balance is 47-53%. Although the Sholes (Qwerty) keyboard fails at conditions A and B (most typing is done on the top row and the balance between the two hands is 57% and 43%), the policy to put successively typed keys as far apart as possible favors factor C, thus leading to relatively rapid typing.44

The explanation for Norman and Rummelhart's factor C is that during a keystroke, the idle hand prepares for its next keystroke. Thus Sholes's decision to solve a mechanical problem through careful keyboard arrangement may have inadvertently satisfied a fairly important requirement for efficient typing.

The consistent finding in the ergonomic studies is that the results imply no clear advantage for Dvorak. These studies are not explicitly statistical, yet their negative claim seems analogous to the scientific caution that one exercises when measured differences are small relative to unexplained variance. We read these authors as saying that, in light of the imprecision of method, scientific caution precludes rejection of the hypothesis that Dvorak and Qwerty are equivalent. At the very least, the studies indicate that the speed advantage of Dvorak is not anything like the 20-40 percent that is claimed in the Apple advertising copy that David cites. Moreover, the studies suggest that there may be no advantage with the Dvorak keyboard for ordinary typing by skilled typists. It appears that the principles by which Dvorak ''rationalized" the keyboard may not have fully captured the actions of experienced typists largely because typing appears to be a fairly complex activity.