Dynamic cursor gain and tactual feedback in the capture of cursor movements.

Recent research involving a trackball with force feedback has demonstrated that tactile feedback can enhance the acquisition of targets in graphical user interfaces in terms of movement times and errors. The present study seeks to explore the degree to which tactual feedback over a target, in contrast to changes in the display/control gain over the target, influences target acquisition performance. Tactual feedback over a target is felt as a pulling force towards the centre of a target, with a counterforce applied when moving out of the centre. Changes in the cursor gain can be used to create a cursor-catching effect by requiring more movement effort of the control device to leave than to enter the target centre, without increasing the total amount of effort to enter and leave the target area. User movement in entering a target is thus braked by the change in cursor gain. Results of an experiment indicated that target acquisition performance was generally higher in the tactual feedback condition, followed by cursor gain feedback, in comparison with no-cursor gain feedback. User interface design issues as related to gain feedback in visual interfaces and tactual feedback over targets are considered.

Directional sensitivity to a tactile point stimulus moving across the fingerpad.

The ability of subjects to discriminate between directions of a point contact moving across the fingerpad was examined. Subjects were required to report, using an adaptive two-interval, two-alternative forced-choice procedure, whether in two sequential stimuli the direction of motion changed in a clockwise or counterclockwise direction. The overall mean orientation-change threshold across eight stimulus orientations was approximately 14 degrees, with the lowest threshold for the point motion toward the wrist. This observed lower threshold in the distal-to-proximal direction is thought to be due to stretching of the skin at the tip of the fingernail, to which one may be particularly sensitive. For all orientations, thresholds were generally more uniform and higher than those reported on vibrotactile linear contactor arrays for horizontal and vertical orientations.