The examination of problem-solving processes continues to be a current research topic in education. Knowing how to solve problems is not only a key aspect of learning mathematics but is also at the heart of cognitive theories, linguistics, artificial intelligence, and computers sciences. Problem solving is a multistep, higher-order cognitive task that permeates a number of disciplines; thus, there is a need for research in this area. To date, most interpretive research studies on problem solving have relied on "think-aloud protocol" or "diary" as introspective methods for examining problem-solving processes. This article describes the investigation of an alternative introspective approach, based on Popper's critical rationalism, to gather data on preservice teachers' problem-solving processes. Twenty-one groups of preservice teachers used this introspective approach to deal with practical assessment issues. Despite research design limitations, this introspective data collection tool shows promise in documenting preservice teachers' collective problem-solving processes. (Contains 1 figure.)