Abstract
Using pinch gestures, i.e., using finger span and hand location to control the size and location of the object simultaneously, is a popular type of interaction in multi-touch applications. However, there is a lack in literature regarding effects of moving amplitude, direction, and target width on performance in time and accuracy for pinch operations. The current study recruited 27 participants to perform a realistic 2D synchronous pinch task with various amplitudes, directions, and target width settings. The results showed that the moving amplitude only affected time but not accuracy, while the direction and target width influenced both. Users tended to perform accurate pinch operations when the target is small, while their accuracy was limited possibly due to biomechanical factors when the target is large. The study also found diagonal movements were beneficial for pinch operations in accuracy, while time performance of lower-right movements in pinch gesture suffered from blocking effect. Implications of those findings in design of multi-touch applications are discussed.