Contact Location Offset to Improve Small Target Selection on Touchscreens

Target size recommendations found in the literature for touchscreen mobile devices take into account finger inaccuracies in order to provide good selection accuracy. These recommendations are violated when a virtual QWERTY keyboard is designed into a mobile interface. Small targets increase the severity of finger occlusion, resulting in higher selection errors. It has been observed that an offset exists between the intended landing location and actual finger contact location. An experiment was conducted to study the contact offset and how it is affected by different target size, gender, finger used, and prior experience using handheld touchscreen device. Results show that irrespective of target size, users tend to aim towards the center of the target, and that an offset exists between the target center and actual contact. Mean value of the offset lies beneath and to the right of the target center for right handed users. Providing this offset globally by shifting the reported finger contact location or locally by shifting the target active area could greatly improve small target selection.