Why can quizzing yourself help more with memory retention than rereading?

Why can quizzing yourself help more than simply rereading? 

In a now-classic UCLA study that has stood the test of time, people tried to answer questions before seeing the correct answers. Even when their first guesses were wrong, they remembered more later than people who only read the material. 

The findings suggest that trying to recall an answer can prepare your brain to learn it. 

Read the entire paper: Unsuccessful retrieval attempts enhance subsequent learning