Students should learn best by repeating a cycle of studying, testing, and feedback, all of which are components of "mastery learning." We performed an archival analysis to determine the relation between taking quizzes early and quiz performance in a "mastery learning" context. Also investigated was whether extra credit resulted in early testing and improved scores on the quizzes. Results, based on data from 270 college students enrolled in 10 sections of Introductory Psychology, suggested that testing sooner is associated with better quiz performance. Providing extra credit resulted in a larger percentage of attempts that occurred during the first 5 days of quizzing but did not result in overall better quiz performance compared to sections not offering extra credit. (Contains 2 tables.)