This research aims to examine touch performance and user-satisfaction depending on key location in a QWERTY soft keyboard during two-thumb key entry on a smartphone. Thirty-three college students who were smartphone users were recruited, and an experimental program was implemented to measure their task completion time, the number of touch errors, and user-satisfaction during key entry. The QWERTY layout was split into 15 zones to assign absolute positions for reliable statistical analysis. The results showed that the zones with significantly longer task completion times were observed more prevalently in the zones in the periphery (p < 0.0001). In addition, relatively higher subjective satisfaction ratings were found in the zones in the center area of the QWERTY layout (p < 0.0001). It seemed that both of the results were improved in the zones that participants could immediately see without moving the thumbs, before touch interaction. Meanwhile, touch error frequencies failed to show statistical significance among the zones (p = 0.3195).

This study investigated the muscle activities, motor variability, and functional connectivity of the upper limb as a function of weight distributions in a handle of a cordless stick-type vacuum cleaner. Eighteen female college students with experience of vacuum cleaner-use participated in testing. Five handles with different centers of mass (CM) were prepared (centroid, top-rear, top-front, bottom-front, and bottom-rear), and electromyography for the muscles of the upper limb were measured during vacuuming. The results showed that the %MVC values of the Extensor Carpi Ulnaris (p = 0.0038) and Deltoid Middle (p = 0.0094) increased but that of the Biceps Brachii (p = 0.0001) decreased, as the CM moved from the top to bottom area of the handle. The motor variability of the Extensor Carpi Ulnaris (p = 0.0335) and Brachioradialis (p = 0.0394) significantly varied depending on the CM locations but failed to show significance in the post-hoc analyses. Lastly, the functional connectivity values of the muscle pairs such as the Extensor Carpi Ulnaris–Deltoid Middle (p = 0.0016), Extensor Carpi Ulnaris–Upper Trapezius (p = 0.0174), Brachioradialis–Biceps Brachii (p = 0.0356), and Biceps Brachii–Upper Trapezius (p = 0.0102) were significantly altered as a function of the CM locations. The lowest functional connectivity was found with the handle of which CM was at centroid.

This study aims to observe which thumb, the left or right, is used for keystrokes and examine the patterns during two-thumb key entry on a smartphone QWERTY soft keyboard. A total of 36 college students, including 18 left-handed and 18 right-handed, were recruited for testing, and they had 9.7 years of smartphone use experience on average. A smartphone application was implemented, and whether the left or right thumb was used for touch interactions was recorded for each of the 26 letter keys. As a result, it was found that there were slightly more letter keys that were statistically more often tapped by the left thumb during the two-thumb key entry on the QWERTY soft keyboard, regardless of the participant’s handedness. In addition, all the letter keys were touched statistically more often with the relatively closer one of both thumbs, except for the letter keys G and V in the center. It seemed that the distance between keys and thumbs was regarded as the most important factor influencing the thumb choice for keystrokes, followed by the habituated experience of using physical QWERTY keyboards.

1. Touchscreen-based interaction is firmly established as the primary input mechanism underlying most user activities on contemporary mobile devices. Statista (2025) reported that a survey of appro...