This chapter discusses the choice between gambles: a stark contrast exists between integration models such as prospect theory and heuristic models such as the Priority Heuristic. It explores the process tracing data using Mouselab, provides a richer set of data beyond observed choices allowing researchers to sort through alternative explanations more quickly. The chapter explains two important advantages of using process data. First, process tracing facilitates the comparative evaluation of multiple theories. Second, process tracing can help us understand heterogeneity among individuals. The chapter illustrates the advances focusing on two case studies from common decision domains that test specific theoretical accounts and acknowledge individual differences. The PH predictions about the content and sequence of information acquisition are based on the fact that the heuristic identifies a set of reasons to be followed by the decision maker in a specific order.