The present study investigates the human haptic perception of 2.5D dome-shaped surface features in terms of difference and absolute thresholds. We conducted two experiments to measure the thresholds, analyzing the effect of sample base area, or diameter, and surface material compliance. In Experiment 1, the difference threshold for 2.5D surface feature height was measured for three different sample base diameters, 1.4, 2.8, and 5.6 mm. The results indicated a decreasing trend in Weber fraction, i.e., higher sensitivity, with an increase in the sample base diameter. The effect of surface material compliance was found to be insignificant. Further analysis indicated the decreased Weber fraction with an increase in base diameter for shapes with a smaller reference height-to-diameter ratio. However, the effect of base diameter became insignificant for a larger reference height-to-diameter ratio. In Experiment 2, the absolute threshold was measured for three sample base diameters, 1.4, 2.8, and 5.6 mm. The experimental result showed a clear linearly increasing trend in the absolute threshold as the sample base diameter increased, which is consistent with a previous study.
Hwang et al. (Wed,) studied this question.