An experimental comparison of a ternary chord keyboard with the QWERTY keyboard

Chord keyboards use the concept of simultaneous activation of keys to produce single characters. Some chord keyboards have been suggested as potential devices to replace the standard QWERTY keyboard which is now considered the major human-computer interface tool.

This study focused on evaluating a new chord keyboard that uses a set of eight ternary (3 state) keys. An experimental comparison of the ternary chord keyboard (TCK) with the QWERTY keyboard was conducted. Two groups of subjects were selected to participate in the study. One group was assigned to the QWERTY keyboard and the other to the TCK. The two groups learned to input a set of 17 characters. Training of each group was similar and the stimuli were identical. The study investigated how the two groups compared in attaining certain performance criteria (speed and accuracy), and how performances compared on both keyboards after fulfilling the criteria.

For each group, the number of sessions to reach the criteria was recorded along with speed and accuracy of typing. At the end of the experimental session, subjects rated some features of their respective keyboard. Performances on both keyboards were comparable in all stages with no significant differences revealed. However, executing chords on the TCK was rated significantly more difficult than activating keys on the QWERTY keyboard.