  Purpose: The purpose of this study was to investigate the psychophysical
understanding of the slip stimulus. We emphasized that the perception of slip
and its characteristics, such as slip distance and slip speed depend on the
interaction between slip direction, slip distance as well as slip speed.
Methods: We developed a novel slip induction device to simulate the artificial
sense of slip. We conducted a psychophysical experiment on eight healthy
subjects. The experiment was designed to evaluate the effect of slip direction
on slip perception as well as on the perception of slip distance and slip
speed. A series of psychophysical questions were asked at the end of the slip
stimulation to record the subjective responses of the participants. The average
success rate (%) was used to quantify the subject responses. Results: We
demonstrated that the perception of slip is independent of slip direction
however, perception of slip distance and slip speed are significantly modulated
by slip direction. We also observed that a significant interaction exists
between slip distance and slip speed in the upward slip direction. It was also
observed that the average success rate was significantly different for various
combinations of slip distance and slip speed in the upward slip direction.
Conclusions: Our study clearly establishes a significant interaction between
the slip direction, slip distance, and slip speed for psychophysical
understanding of the perception of slip distance and slip speed.
