Under Eliot's leadership, Harvard adopted an "elective system" which vastly expanded the range of courses offered and permitted undergraduates unrestricted choice in selecting their courses of study — with a view to enabling them to discover their "natural bents" and pursue them into specialized studies. A monumental expansion of Harvard's graduate and professional school and departments facilitated specialization, while at the same time making the university a center for advanced scientific and technological research. Accompanying this was a shift in pedagogy from recitations and lectures towards classes that put students' achievements to the test and, through a revised grading system, rigorously assessed individual performance.