This chapter explores under what conditions participants generated valid reports of thoughts that mediated their production of actions. It describes a general rigorous methodology for collecting, transcribing, and encoding verbalizations of thoughts as reliable and valid data. The chapter discusses the methodological problems of collecting and analyzing verbal reports in the more history of psychology and explains how many of these problems are addressed by methodological approach. It shows how recommended approach minimizes reactive effects of verbalization on performance. The chapter describes the practical recommendations for how to instruct participants and how to remind them to keep verbalizing without reactive effects on the thought processes. A completely different approach was needed, where investigators tried to describe the sequence of verbalized thoughts that humans reported mediated their decision making. The chapter also discusses how some of the methods to establish validity of verbally reported information on decision making have been compromised by the types of tasks selected for study.