Collaborative exams, with subsections in which students have an opportunity to work with each other, are not yet widely used in introductory geoscience courses. This type of exam structure, with other participatory teaching strategies, was employed in two different courses, and results were found to provide a sensitive and revealing tool for analyzing the progress of students' individual and collaborative learning throughout the semester. A somewhat different implementation of the collaborative exams in each course showed that overall student performance was significantly improved compared to performance in the individual part, even for middle and highest-achieving thirds of the student population, and progressive improvements in performance were followed through the semester. The implementation of collaborative exams in the first course involved an aspect of exam grading that provided an incentive for collaboration: the "jackpot effect," which provided insight into the dynamics of peer interaction. The simpler implementation in the second course used a different approach in which the collaborative tests were less important to the total class grade, but also showed improvement in students' individual performance. Wider application of these methods could make a critical difference in reversing student apathy toward science in colleges and universities.