Comparing the Psychophysical Capabilities on Fingertip and Wrist using Method of Adjustment

Haptic technology, which refers to creating the sense of touch artificially, offers a crucial source of communication between humans and computers or machines. While conventional haptic devices are designed to render vibrotactile information on the fingertip, recent trends in the field expand the tactile communication to other body locations, like the wrist. Even though the literature has many successful applications showing the validity of such haptic applications, there is no study comparing the user perception for meaningful virtual or teleoperated task scenarios due to the lack of calibration methods between alternative body locations. In this paper, we attempt to compare the perceived intensities at the fingertip and the wrist through psychophysical experiments and to answer: (i) Is there a perpetual difference between the haptic stimuli on the wrist compared to the fingertip? (ii) Is possible to form a reasonable, linear relationship (or a pattern) between the stimuli rendered at the fingertip and the wrist? (iii) If so, do different users require different relationships that would need to be obtained through calibration? We designed a user study with 13 healthy participants, receiving three levels of haptic stimuli at their fingertips while adjusting the intensities of the stimuli rendered at their wrist using the method of adjustments. Our results indicate that there is a linear pattern between the vibrotactile stimuli rendered at the fingertip and the wrist, and each participant exhibits a different pattern. Our results can be used to equalize the perceived intensities of different forms of tactile stimuli for future research investigating the perceived performance under different haptic scenarios.