Force JND for Right Index Finger Using Contra Lateral Force Matching Paradigm

Abstract

The paper aims at deriving the Just Noticeable Difference (JND) for force magnitude recognition between left and right index finger of human hand. The experiment involves establishment of an internal reference stimulus, using the left index fingers of the hand, by the subject, which is perceived and matched under contra-lateral force matching paradigm. A combination of virtual environment and a force sensor was used to derive the just noticeable difference for index-finger force application. Six voluntary healthy young adult subjects in the age group of 22–30 years were instructed to produce reference forces by left index finger and to reproduce the same amount of force by the right index finger, when the subjects were confident enough of matching same amount of force, the force values of the both the left and right index finger were recorded simultaneously for 5 s at 10 Hz. Five different trials were conducted for different force levels ranging from 2 to 5 N. The percentage real JND and absolute JND were derived for all the subjects. It was found that the Force-JND obtained was approximately 10 % across all subjects. Results also show that subjects tend to underestimate force at high force levels and overestimate at low force levels. The results obtained can be used as basic building block for the calibration of virtual reality based minimally invasive surgery related tasks and force based virtual user interfaces ranging from touch pad to assistive tools.