The relation between category and magnitude estimates of tactile intensity

The effect of various types (sandpaper, spoke, spiral, and white) and speeds (0, 1/2, 3, 6, 12, and 30 rpm) of rotating disk backgrounds upon 276 Ss’ estimates of the apparent verticality of a line moved toward physical verticality in either a clockwise or counterclockwise direction was investigated. The general finding was that the estimate of verticality was displaced away from pretest judgments in the direction of the disk rotation. The speed of rotation was significant with maximal vertical displacement at 6 rpm. The direction of line movement was significant with the result that maximal vertical displacement occurred when the line was moved in opposition to the direction of disk rotation. The type of disk employed made a significant difference in the estimates only when the line movement was opposite from the direction of disk rotation. Disks with inadequate stimulus contours (white) produced no significant effect. Results are discussed in terms of stimulus contour and ocular torsion.