A mathematical model based on queuing theory is used to study the dynamics of environmental influence on twin pairs. The model takes into consideration genetic factors and effects of non-shared environment. Histograms are exploited as base analysed characteristics, with the method of minimum chi-square yielding estimated characteristics. The proposed technique was applied to analysis of longitudinal data for MZ and DZ twins. It was shown that the same environment impact may yield different contributions to final variances of the IQ parameters under investigation. Magnitudes of these contributions depend on the genetic factor represented by distributions of an analysed parameter at the point of birth. Twin Research (2000) 3, 92–98.
