A Systematic Approach to Characterizing Smartphone Icon-Touching Performance

The size of a touch icon is a critical factor affecting smartphone use performance. The existing literature recommends a 10-mm icon side/diameter for a successful touch. Though this can be applicable in routine use, there are circumstances where smaller icons are required. Two experiments were conducted to systematically investigate the effects of icon size and spacing on touch performance: one experiment for square icons and the other for circular icons. The icon size ranged from 2 to 11 mm, while spacing ranged from 0 to 8 mm, depending on icon size. Seventy-five combinations of icon size and spacing were randomly presented on a smartphone. The subjects’ task was to touch an icon as soon as it occurred. Performance was measured with a hit rate for icons and with icon-touch time. A change-point detection algorithm was developed to characterize the icon-touch performance. The results show that icon hit rate increased and icon-touch time decreased with an increase in icon size; a change point in the icon hit rate was identified around the icon size of 6 mm; icon spacing had no significant effect on icon hit rate or icon-touch time. To conclude, smartphone icon-touching performance can be comprehensively characterized using the systematic approach developed in the present study.