Target selection on hand held tablets

The use of mobile devices has been increasing and besides mobile phones, other devices have strongly established themselves in the market, that is the case of tablets. Although tablets might seem similar to modern-day smart phones the truth is that both kind of devices have differences that make their users interact with them in different ways. For instance, the size of a tablet is larger than that of a smart phone and that leads to differences in the grasp, that for a tablet results better to hold it with both hands. As a result of this two-handed grip, it is only possible to operate the device with the thumbs. Although there is already some body of work that has studied the target selection times with tablets using this kind of grip, nothing has been researched so far about a distinction and influence of the angle of approach to such targets. We believe that the biomechanical configuration of the hand leads to differences in the selection times when moving the thumb since it can be observed that the thumb cannot move towards certain regions with the same ease than when it moves to other positions. We have planned and designed an experiment that evaluates the thumb selection times for different angles while on a tablet that is grasped with both hands in landscape mode. Our target was to determine if there are differences in the time to reach a target between different angles of approach. Finding these differences would help to define a proper model that describes such behavior and also understand for which conditions of angle and amplitude it is easier or more difficult for users to interact with these touch screen devices. We also analyzed if the direction of the trajectory followed by the thumb had an influence and could determine which areas and movements of the thumb correspond with fewer errors and fastest times during target acquisition