Effect of touch coordinate display as a form of augmented, concurrent visual feedback on the accuracy of single-handed typing via smartphone virtual keyboards

This study assessed the effect of an easily perceived real-time visual feedback method on touchscreen typing accuracy. Thirty subjects were asked to hold a smartphone with a capacitive touchscreen in one hand and enter a text using the thumb of the same hand via a custom designed virtual keyboard. There were two types of text entry sessions: with or without visual feedback. The visual feedback consisted of a full-screen crosshair, representing the accurate coordinate of touch in real time. In each session, touch-down time on the virtual keyboard and touch coordinates were recorded for every touch action. Two types of typing errors were defined: 1) centering error (CE), which was calculated as the mm distance between the coordinate of the touch and the center of the key, and 2) incorrect entry (IE), which was the number of missed keys. Student t-tests and Wilcoxon tests were used for mean and mean-rank comparisons of CE and IE, respectively. The results showed that visual feedback decreased CE (mean SD) significantly from 1.34 +/- 0.38 mm to 0.85 +/- 0.24 mm (P < 0.0005), and decreased IE (median and range, # of incorrect entries) significantly from 5.50 and 32.00 to 1.00 and 7.00 (P < 0.005). In conclusion, the accurate, easily perceived, and 2D real-time feedback decreases touch-typing error rates markedly and therefore can be of practical importance for increasing the productivity of smartphone users.