Central pockets were defined as small, loop-enclosed whorls whose quantitative values must not exceed the third part of the quantitative value of the loop or as small, whorl-like patterns in the core of a loop having at least one curved ridge with its convexity towards the opening of the loop. Applying this classification scheme, the frequency of central pockets was found to be 17.5% in 200 males and 17.0% in 200 females, but was significantly higher in a sample of 21 male and 22 female pairs of MZ twins (33.2% and 34.1%, respectively). Twin as well as family data (94 families with 269 children) pointed to a rather weak hereditary influence upon the formation of central pockets. Rudimentary central pockets occurred in 9.5% of males and 10.0% of females. Since no common genetic basis could be established for central pockets and rudimentary central pockets, the latter should not be scored as central pockets.
