Hierarchical models are linear sequential models built on an assumption that consumers move through a series of cognitive and affective stages culminating in the purchase decision. The common theme among these models is that advertising operates as a stimulus and the purchase decision is a response. A number of hierarchical models can be found in the literature including Lavidge's hierarchy of effects, DAGMAR and AIDA and other variants. Some authors have argued that, for advertising purposes, the hierarchical models have dominated advertising theory, and that, of these models, the AIDA model is one of the most widely applied.