Benjamin Bloom, an important educational psychologist at the University of Chicago in the late 1940s and 1950s, led a team of colleagues in designing what is known as Bloom's taxonomy, a system of classifying goals for the learning process, now used at all levels of education to define and describe the process that students use to understand and think critically about what they are learning.

Bloom identified six levels of learning, as represented in the triangle shown in Figure 10.2. The higher the level, the more critical thinking it requires.