Metacognitive ability- proficiency in analyzing ones own thought processes - is related to the ability to correctly gauge one's mastery of a task (Kruger, 1999; Dunning, 2003). It may also be tied to the ability to make radical conceptual changes - learning new information incongruous with prior beliefs. We hypothesize performance on an expanded version of the Cognitive Reflection Test (Frederick, 2005), a battery of questions designed to measure metacognitive ability, would be a predictor of the extent to which undergraduate college students (N=103) improved their understanding of evolution after a semester of college level biology, particularly in the Darwinian principles behind natural selection such as inheritance, variation, and superfecundity. The benefits should be most pronounced in subjects displaying greater metacognitive ability whose prior knowledge incorporated flawed beliefs such as LeMarckianism or needs-based evolution. If metacognitive ability is indeed predictive of learning, it would suggest conceptual change is facilitated by a disposition to think about one's own concepts. It would also suggest that the quality of education in fields such as biology may be improved by fostering and encouraging more reflective thinking.