Force-Direction Discrimination is Not Influenced by Reference Force Direction (Short Paper)
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The authors report an experiment in which twenty-five participants discriminated force vectors presented along five directions (up, left, right, diagonally up left, diagonally up right). The force vectors were presented with a three degree-of-freedom forcefeedback device. A three-interval one-up three-down adaptive procedure was used. The five reference force-direction conditions were presented in randomly interleaved order. The results show an average force-direction discrimination threshold of 33° regardless of the reference-force direction. Position data recorded at a nominal sampling rate of 200 Hz revealed a 10.1 mm average displacement of the fingertip between the start and end positions in a trial. The average maximum deviation from the starting position within a trial was 21.3 mm. We conclude that the resolution with which people can discriminate force direction is not dependent on the direction of the force per se. These results are useful for designers of haptic virtual environments.