Professor Romano looks at ways to improve student learning. She gives half of her students practice quizzes with only multiple choice questions. She gives the other half of her students practice quizzes that also include short answer questions. Then she looks at how students perform on the exam and sees that students who saw the short answer questions performed significantly better on the exam than students who only saw multiple choice questions. But it turns out that the students who saw the short answer questions also spent longer on the practice quizzes than students who only saw multiple choice questions. This last sentence refers to what concept, most specificall