Structured exploratory data analysis (SEDA) of finger ridge‐count inheritance: II. Association arrays in parent‐offspring and sib‐sib pairs

Familial similarity of the dermatoglyphic trait values of finger ridge‐count scores and pattern intensity index is examined for 125 nuclear families from the Velanadu Brahmin population of Southern India by the method of association arrays. This methodology assesses parent‐offspring and sibship similarity through a collection of measures of dependence that is sensitive to a variety of nonlinear trends and stochastic relationships between trait values. The method is used in conjunction with various weights to determine the relationship between family size and the level and form of dependence. These analyses reveal that siblings are most strongly associated for ridge‐counts of the middle digit and less associated for the thumb and fifth digit ridge‐counts. Further, sibship similarity for ridge‐counts increases with family size for the thumb and fifth digit but remains relatively constant over all family sizes for the middle finger. Family size effects are also observed for total ridge‐counts of the left hand, right hand, and both hands combined, and for the pattern intensity index. These effects of family size may be due to the most pronounced changes occurring in the amniotic environment between the first and second pregnancy, which are most strongly manifested in the sibship associations of smaller families.