The study of communication is elemental to the social sciences but fraught with difficulty. In this book a method that merges statistical modeling along with communication and social network analysis is developed and applied to the complex arena of behavior change. The methodology is used to study changes in the fertility behaviour of women in rural Bangladesh. The total fertility rate fell by 48% from 6.3 in 1975 to 3.1 in 2000. This could not be explained by the notions of economic development instead the answer was sought into an ideational shift formed by communication demonstrating the benefits of smaller family. Data were gathered using structured interviews of village women and the application of the methodology proved that fertility behaviour in rural Bangladesh is a manifestation of ideational change to a small family norm, promoted via an all- out communication campaign using both mass media and interpersonal mechanisms. This involved the use of three interrelated concepts – ideational change, social interaction and social networks. The book will be of interest to those in social sciences, community health and economic development.