A Comparison of Two Chord Keyboard Coding Systems for Alphanumeric Data Entry.

Chord keyboards are alphanumeric data entry devices that generally have fewer keys than a standard typewriter keyboard. Characters are produced by pressing either a single key or several keys simultaneously. Two coding systems, both using one-handed operation, were implemented on a commercially available chord keyboard, the Microwriter. The coding system resident on the Microwriter was compared to the coding system developed by Sidorsky 1974, known as the Alpha-dot system. Measures of time to learn, time to reach a 35 character per minute criterion entry rate, text entry speed and accuracy, and cognitive workload were collected from two groups of ten subjects. Cognitive workload was measured using two auditory tasks in a secondary task paradigm. The results of initial code learning indicated that the two groups did not differ in the amount of time needed to reach a 95 percent accuracy criterion. The Alpha-dot group was, however, quicker in reaching the 35 character per minute speed criterion. Text entry was measured three times during the experiment. The first test, immediately after initial learning of the codes, indicated that the Alpha-dot group was typing at a faster rate, with no difference in errors. The second and third tests showed no differences in speed or accuracy. Based on secondary task performance, the Alpha-dot chord system appeared to require less cognitive workload than the Microwriter chord system.