The study of the perception of forces has a long tradition in experimental psychology. Many studies have shown that forces are perceived through sensations generated by the motor commands producing the effort or motion and not from peripheral information coming from the muscles, the joints, and the skin. Generally, force experiments consist of pairing a weight held contralaterally by an equivalent weight. In the present experiment, the perception of forces was studied in terms of both amplitude and direction. More specifically, the perception of the amplitude and the direction of a force exerted by the thumb was studied in eight different directions.
Some directions give identical behavior while others offer a different behavior.
This convenience sample consisted of college students in occupational and physical therapy with no history of neuromuscular or orthopedic problems. The experimental protocol consisted of studying two conditions, eight directions, and the force was evaluated twice. Under the first condition, the subject was asked to exert a controlled force in a given direction with the thumb of the dominant hand, and then to reproduce the same force in the same direction with the thumb of the nondominant hand. For the second condition, the subject was asked to exert a controlled force in a given direction with the thumb of the nondominant hand, and then to reproduce the same force in the same direction with the thumb of the dominant hand. The degrees indicated apply to the right hand while for the left hand, the data were transformed by symmetry with respect to the vertical axis in order to have directly comparable data for both hands.