The observed physical characteristics of galaxies are (at least partly) determined by the influence of the surroundings after the formation of the galaxies. The examination of the frequency of the occurence of active galaxies, i.e. Seyfert galaxies, in different galaxy systems compared to a sample of field galaxies gives possibly an insight into this problem.
The galaxy groups were taken from the CfA redshift survey, the list of them is published in Mahtessian (1992, Soob. Byurakan. Obs. 65).