Using multilevel models, this study examined "whether" and "why" the strength of association between student-faculty interaction and student cognitive skills development varies across academic majors. The study utilized data from the 2008 University of California Undergraduate Experience Survey (UCUES) and a sample of 43,014 students from 119 academic majors across nine campuses. The results indicate that the impact of interaction with faculty on students' cognitive skills development significantly varies by academic major. Findings also suggest that some aspects of departmental climate can potentially magnify the effects produced by student-faculty interaction. (Contains 2 footnotes, 5 tables, and 1 figure.)