Colemak Mod-DH

A Colemak mod for more comfortable typing.

(rev 2)

Colemak Mod-DH - How easy to learn?

On this page is a consideration of how relatively easy or difficult various keyboard layouts are to learn, assuming a starting point of Qwerty. A commonly used measure is to count how many keys change position. Perhaps sometimes people also consider the number of keys that move to a different finger. But I think it would be useful to have an overall measure of how difficult to learn (i.e. how different) a layout is, which would take into account various relevant factors, to produce well-defined "switching difficulty index".

Consider if you were to move the E key on your keyboard. Because E is so common, it would be extremely disruptive and would take a long time to be able to type efficiently again with it in a new location. On the other hand, if you were to move say, J, the impact would be minimal since it's so rarely typed. It seems that there are at least two factors to consider: both how much a key moved (for example, whether it's on the same finger, or same hand), and also the frequency with which that key is typed.

Caveat: Of course, it's impossible to come up with a perfect system of measuring something as hard to quantify as how difficult something is to learn. Presented here is just one such proposal.

The Switching Difficulty Index

I propose the following scheme which would be used to measure how "different" two layouts are - or to put it another way, how difficult it would be to learn one from the starting point of another (usually Qwerty!). When comparing the two layouts, consider each each key, and give it a movement score (m), from easiest to hardest, as follows:

0 = not moved / angle mod only.
0.25 = moved but same finger.
0.50 = moved to new finger on same hand.
0.75 = moved to equivalent finger on other hand.
1.00 = moved to other finger on other hand.

Then, for each key we multiply by that letter's frequency (f). This gives a final formula for the "switching difficulty index" (d) of a keyboard layout:

d  =  Σ (m * f )

For the purposes of this analysis I am considering only the 30 keys in the main section of the keyboard. Calculating d for a selection of keyboard layouts gives these results:

Results

Keys
Moved
Finger
Keys
Moved
Total
Keys Moved
Index
Σ m
Switching
Difficulty
Index (d)
Qwerty (base) 0 0 0.00 0%
Minimak-8key 3 8 3.50 20%
Qwpr 2 11 4.25 23%
Asset 6 15 6.25 23%
Norman 4 15 5.75 24%
Colemak 12 17 8.00 36%
Mod-DH 12 19 8.50 38%
Workman 13 21 10.00 41%
qgmlwyfub 17 20 12.25 53%
Dvorak 26 28 22.25 66%
MTGAP 21 28 18.50 68%
Comparison of switching difficulty for various layouts, assuming Qwerty as the starting point.

As you might expect, the less optimized layouts such as Minimak, Asset and Qwpr are the easiest to learn. Of the fully optimized layouts, Colemak is easiest, with Mod-DH slightly more difficult (primarily due to its relocated H), but according to these results is still easier to learn than Workman. Predictably, the more radically changed layouts Dvorak and MTGAP are the most difficult to learn.

Although the results pretty much confirm what you might expect from glancing at the various layouts, I think it is useful to have a well-defined measure for layout designers. Perhaps also you might find this measure useful if you are deciding which layout to learn and want to consider the learning difficulty in addition to the benefit gained.

For an assessment of the effectiveness of the various layouts, see this comparison.