Figure 3: Mean finger ridge density (RD) of 10 fingers for each area. R, right hand; L, left hand; arabic number (1, 2, 3, 4, 5); fingers (thumb, index, middle, ring, little); u, ulnar RD; r, radial RD. In both sexes, the thumb and index fingers of both hands show lower RD in the radial and the ulnar areas than middle, ring, and little fingers. For each sex, the radial and the ulnar RDs were not statistically different (P = 0.863 in boys; P = 0.294 in girls).