A great deal of conceptual clarity was introduced into the study of marriage by the direct observation of marital interaction and by the notions of adaptive probabilism. One of the major points I wish to make in this book is that it was not at all obvious what to study in marital interaction, or even what to consider positive and negative. For example, are interruptions, disagreements, anger expressions, and not looking at the speaker positive or negative? These things have to be determined empirically.