Critical thinking is a valued educational outcome; however, little is known about whether psychology courses, especially ones such as research methods courses that might be expected to promote critical thinking skills, actually improve them. We compared the acquisition of critical thinking skills for analyzing psychological arguments in 3 groups of research methods students, 1 getting critical thinking skills infused directly into their course and 2 other groups getting no explicit critical thinking skills instruction. We found that the group receiving explicit critical thinking skills instruction showed significantly greater gains in their argument analysis skills than the groups receiving no explicit critical thinking instruction. These results support the effectiveness of explicitly teaching critical thinking skills infused directly into regular course instruction. (Contains 3 notes and 1 table.)