Experiental learning theory (ELT) defines learning as a process of acquiring knowledge through the transformation of experience. Four different types of learner can be distinguished: convergers, who gain knowledge by abstract conceptualization and active experimentation; divergers, who use concrete experience and reflective observation; assimilators, who tend to learn by abstract conceptualization and reflective observation; and accommodators, who prefer learning by concrete experiences and active experimentation. The theory was popularized by David Kolb, and is largely based on the work of Kurt Lewin, John Dewey and Jean Piaget.