Faculty rely on quizzes for a couple of reasons. They motivate most students to keep up with their class work and, if they're unannounced, they motivate most students to show up regularly for class. The research on testing offers another reason, something called “the testing effect,” described as “the phenomenon in which people appear to retain more information about a topic if they are tested on that topic and engage in memory retrieval of topic information than if they simply reread or study that information.” (p. 174) It's the idea behind practice tests.
