Social influence network theory is based on three constructs – persons' attitudes, susceptibilities, and interpersonal influences. In the previous chapter, we focused on the mechanism underlying attitude changes that result from endogenous interpersonal influences. Under the assumptions of our standard model, this mechanism is y(t + 1) = AWy(t) + (I − A)y(1). Here we focus on the substantive foundations and operationalization of the constructs involved in this mechanism. Theories may be interesting, but to be useful they need to be operationalized. The domain of operationalization includes not only the possible substantive realizations of the theoretical constructs but also the measurement models for these substantive realizations. There is an intimate dance between theory and measurement, and we devote the present chapter to this pas de deux.

The first construct, y(t), defines the substantive domain of our theory, i.e., the n × 1 array of group members' attitudes on an issue at time t. We see the substantive domain of our theory as large. The theory deals with attitudes and their change, but it also encompasses other cognitions that are not easily subsumed by the conventional definition of attitudes as a positive or negative evaluation of an object. Here, we will describe the attitude construct in the general form in which we employ it, and provide several realizations of the construct that are consistent with our specification.