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Manual discrimination of force using active finger motion.
X D Pang1, H Z Tan, N I Durlach
1Massachusetts Institute of Technology, Cambridge 02139.
Perception & Psychophysics
|June 1, 1991
Summary
Human subjects can detect a force difference of approximately 7% when squeezing objects. This study measured the just noticeable difference in grip force discrimination across various force, distance, and velocity parameters.
Area of Science:
- Human motor control
- Psychophysics
- Biomechanics
Background:
- Understanding the human capacity for force discrimination is crucial for designing effective human-machine interfaces and rehabilitation tools.
- Previous research has explored tactile and force perception across different body parts and using various methodologies.
Purpose of the Study:
- To quantify the just noticeable difference (JND) in grip force discrimination using a thumb-and-forefinger grasp.
- To investigate the influence of force levels, squeeze distance, initial fingerspan, and squeeze velocity on force perception.
Main Methods:
- An electromechanical system applied constant resistance forces during a linear squeeze task.
- Subjects discriminated between a reference force and a reference-plus-increment force.
- A one-interval psychophysical paradigm with trial-by-trial feedback was employed.
Main Results:
- The just noticeable difference (JND) for grip force was found to be approximately 7% of the reference force.
- This finding held across tested ranges: 2.5–10.0 N (force), 5–30 mm (distance), 45–125 mm (initial fingerspan), and 25–160 mm/sec (velocity).
Conclusions:
- The human ability to discriminate grip forces is robust across a range of physical parameters.
- Results align with prior psychophysical findings on tactile and force perception in other contexts.