Testing the usability of smartphone surface gestures on different sizes of smartphones by different age groups of users

This study focuses on testing the usability of 3 different sizes of smartphones by children, adults, and the elderly. Forty-seven participants from each age group were recruited. The research consisted of two stages of experiments. In the first experiment, three existing gestures used by the Android system were evaluated: drag, pinch, and double-touch drag. In the second experiment, two additional re-design gestures were tested: multi-long press and slide down. The users' performances were measured based on their overall time, success time, accuracy, Fitts' Law values, and a subjective questionnaire. Among the five gestures, drag and multi-long press were categorized as the drag gesture, and pinch, double-touch drag and slide down were categorized as the enlarging gesture. The results show that children and adults outperformed the elderly in gesture operation. With respect to smartphone size, the subjects had faster response times and better Fitts' Law values on 6-inch phones. When comparing the subjective preference and the objective use measurement values of the two drag gestures and three enlarging gestures among the different age groups, it was found that children and adults were consistent, whereas the elderly were inconsistent. Overall, in operating the original drag and pinch gestures, the elderly exhibited better objective use measurements, but they preferred the improved gestures, such as slide down.