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Effects of Mental Practice and Body Position on the Accuracy of Blind Visual-Kinesthetic Positioning

Ware (2) and Ware and Barnhill (3) have demonstrated that practice alone with indirect subject control and practice with different types of sensory feedback and direct subject control leads to an increase in the perceptual accuracy of intermediate visualkinesthetic position. The research was conducted while the subject was sitting with head tilted or standing. The present study extended practice to include mental practice (1) and to include the supine as well as the standing position. Fifty-two undergraduate psychology students from 18 to 44 yr. of age were randomly assigned to a mental practice or a control condition. Within each condition, half of the students performed in the standing and then the supine position and the others in the opposite order. Details of the apparatus were described earlier (3). The device was 4 ft. in diameter with a double-pointed rod that pivoted in the middle to allow free movement around 360". All students, tested individually, were shown that device. Control students were allowed l0'min. to relax before performing while the other students were guided through 10 min. of mental practice on the device. The students were then blindfolded, and the device was adjusted so the center of the rod was parallel to the base of the sternum. Starting in a standing or supine position, they adjusted the rod randomly to the 12 clock positions. Seventeen practice trials and 12 test trials were given for each of the body positions. Accuracy was measured in degrees discrepancy from the assigned clock positions. The amount of mental practice used here was not effective in significantly increasing blind positioning accuracy. Subsequent research might focus on more mental practice time and actual performance before mental practice. The positioning accuracy for the standing position was, however, significantly better than the supine body position using constant errors (PI,* = 8.00, P < .01), with means and standard deviations, respectively, being M = -2.83, SD = 2.93 and M = -5.08, SD = 2.80. A significant interaction was found between position and trials (&.a = 7.31, P < .01). The difference between the means in the vertical body positions for the practice trials (M = -2.85, SD = 2.36) and the test trials (M = -2.82, SD = 3.17) was minimal, while the difference between the means in the supine position (M = -5.53, SD = 6.28) and (M = -4.62, SD = 4.84) indicates some learning. The unfamiliarity of performing blindfolded plus being in a supine position may have accounted for the significant main effect. Research should test the effect of extended blind training while supine on positioning accuracy.