This study compared changes in psychology and philosophy classes in two distinct components of critical thinking (CT): general skills and personal beliefs. Participants were 128 undergraduates enrolled in CT in psychology, other psychology courses, or philosophy courses. CT and philosophy students significantly reduced beliefs in paranormal phenomena at the end of the semester compared to other psychology students. Only philosophy students improved on the Watson-Glaser Critical Thinking Appraisal. The Watson-Glaser may not fully measure CT emphasized in psychology, but psychology instructors can still effectively teach students to examine their own beliefs and think differently in their daily lives. Differentiated assessment of CT is important as instructors evaluate student learning against specific goals.