Structure of Hand/Mouse Movements

This study investigated the distribution of movement time (MT) and submovement time as a function of Fitts´ index of difficulty (ID) to help understand the underlying mechanisms of Fitts´ law. Many previous studies have shown that movements in such a task can be broken into a series of submovements, but have not been able to account for the variation of MT with ID under different conditions and for different tasks. The trajectory of computer mouse movements was recorded and analyzed to identify the distribution of submovements and MTs. The movement trajectory consists of a series of submovements with predictable probabilities. The first submovement is ballistic in nature and has an initiation time proportional to the movement amplitude. The verification time is dependent on target size. The probabilities of occurrence of each submovement can account for the variations in MT. The developed method has application to the evaluation of computer input devices, as the structure of the movement shows the ability of a person to control a device to minimize the time for movement.