Changes in applied force to a touchpad during pointing tasks

We measured the force applied to a touchpad during pointing tasks for large and small targets. A mouse was also used as a baseline condition. Our set-up to measure force included a Plexiglas plate mounted on a high-sensitivity three-axis strain gauge connected to an instrumentation amplifier and a data acquisition computer. The devices were positioned and operated on top of the plate with the selection button removed and actuated by the opposite hand. An experiment used 12 participants performing point-select tasks in conformance with ISO 9241-9. At the terminal phase of the selection tasks, the applied force with the touchpad was lower than that recorded with the mouse. These differences may be the source of overall performance differences between the two devices. It is suggested that the detected finger force should be a variable in the touchpad's transfer function to afford a better blend of coarse and fine positioning strategies, with the coal being to bring the touchpad more inline with the mouse in overall user performance.