Environmental and sibling resemblance components of variance and covariance in traits of early child development.

The multiple regression analyses were undertaken to elucidate the significance and relative importance of different potential determinants of several child development traits (i.e. age at which child 1. turns himself over; 2. sits up; 3. stands up; 4. walks, and 5. cuts his first tooth). Despite the fact that we used a relatively wide gamut of potential determinants (such as parental age, geographic origin, occupation, current residence, or family size) of trait variability, the results of multiple regression analysis (N = 300 families) indicate an almost complete absence of significant factors and studied variables of development. Sibling resemblance component of variance and covariance for five mentioned traits of development and some morphological characters (weight, length and head circumference at day of birth and at 16 months) were studied in 66 families. The transmissibility ("heritability") values for the development traits were small, ranging from 0 ("Turn") to 0.42 ("Walked"). The Findings suggest that there are significant inverse relationship between some of the developmental traits and inborn morphological characters.