This research monograph describes a new approach to the measurement of thinking processes. The author begins with a discussion of the logic of thought versus the psychology of thinking. Traditionally, thinking has been defined in terms of the logical thought processes which lead to warranted conclusions. The psychological processes, on the other hand, involve the individual's perceptions, intentions and information-processing strategies. Traditional logical approaches appear to be most suitable for analysis of thinking in formal highly structured problem situations. Current tests of critical thinking reflect the logical approaches to measuring thinking; two tests of this type are evaluated by the author. The authors define the information-processing approach to measurement of thinking, which emphasizes the way situational information is perceived, selected, organized and interpreted. Using this approach, the authors have developed two interpretive exercises, The Holocaust and The Bomb Factories. The results of a number of studies conducted with these exercises are presented, and future work is projected.