ABSTRACT
This chapter describes an additive stage process model that identifies some of the mental operations of question answering. The model is called VAIL, because it was originally developed to address the "verification of the assertions and implications of language". VAIL is evaluated with respect to some experiments conducted in the laboratory. These experiments examined the verification of sentences about the assertions and implications of a message, the answering of yes-no questions, the answering of wh- questions, and the answering of questions about brief passages. The chapter examines certain issues of question answering that are not directly addressed by VAIL. The crucial assumption of VAIL is that response latency reflects the execution of a sequence of processing stages whose durations are additive. The accuracy of many of the predictions derived from the model indicates that the application of VAIL to question answering is a useful endeavour.
