Basic Research and Implications for Educational Practice

A powerful way of improving one’s memory for material is to be tested on that material. Tests enhance later retention more than additional study of the material, even when tests are given without feedback. This surprising phenomenon is called the testing effect, and although it has been studied by cognitive psychologists sporadically over the years, today there is a renewed effort to learn why testing is effective and to apply testing in educational settings. In this article, we selectively review laboratory studies that reveal the power of testing in improving retention and then turn to studies that demonstrate the basic effects in educational settings. We also consider the related concepts of dynamic testing and formative assessment as other means of using tests to improve learning. Finally, we consider some negative consequences of testing that may occur in certain circumstances, though these negative effects are often small and do not cancel out the large positive effects of testing. Frequent testing in the classroom may boost educational achievement at all levels of education. In contemporary educational circles, the concept of testing has a dubious reputation, and many educators believe that testing is overemphasized in today’s schools. By ‘‘testing,’’ most commentators mean using standardized tests to assess students. During the 20th century, the educational testing movement produced numerous assessment devices used throughout education systems in most countries, from prekindergarten through graduate school. However, in this review, we discuss primarily the kind of testing that occurs in classrooms or that students engage in while studying (self-testing). Some educators argue that testing in the classroom should be minimized, so that valuable time will not be taken away from classroom instruction. The nadir of testing occurs in college classrooms. In many universities, even the most basic courses have very few tests, and classes with only a midterm exam and a final exam are common. Students do not like to take tests, and teachers and professors do not like to grade them, so the current situation seems propitious to both parties. The traditional perspective of educators is to view tests and examinations as assessment devices to measure what a student knows. Although this is certainly one function of testing, we argue in this article that testing not only measures knowledge, but also changes it, often greatly improving retention of the tested knowledge. Taking a test on material can have a greater positive effect on future retention of that material than spending an equivalent amount of time restudying thematerial, even when performance on the test is far from perfect and no feedback is given on missed information. This phenomenon of improved performance from taking a test is known as the testing effect, and though it has been the subject of many studies by experimental psychologists, it is not widely known or appreciated in education. We believe that the neglect of testing in educational circles is unfortunate, because testing memory is a powerful technique for enhancing learning in many circumstances. The idea that testing (or recitation, as it is sometimes called in the older literature) improves retention is not new. In 1620, Bacon wrote: ‘‘If you read a piece of text through twenty times, you will not learn it by heart so easily as if you read it ten times while attempting to recite from time to time and consulting the text when your memory fails’’ (F. Bacon, 1620/2000, p. 143). In the Principles of Psychology, James (1890) also argued for the power of testing or active recitation: A curious peculiarity of our memory is that things are impressed better by active than by passive repetition. I mean that in learning (by heart, for example), when we almost know the piece, it pays better to wait and recollect by an effort from within, than to look at the book again. If we recover the words in the former way, we shall probably know them the next time; if in the latter way, we shall very likely need the book once more. (p. 646) Bacon and James were describing situations in which students test themselves while studying. We show later that their hypotheses are correct and that testing greatly improves retention of material. However, we need to make a distinction between two Address correspondence to Henry L. Roediger, III, or to Jeffrey D. Karpicke, Department of Psychology, Box 1125, Washington University in St. Louis, One Brookings Dr., St. Louis, MO 63130-4899, e-mail: [email protected] or [email protected]. PERSPECTIVES ON PSYCHOLOGICAL SCIENCE Volume 1—Number 3 181 Copyright r 2006 Association for Psychological Science at Harvard Libraries on July 13, 2010 pps.sagepub.com Downloaded from types of effects that testing might have on learning: mediated (or indirect) effects and direct (unmediated) effects. Let us consider mediated effects first, because testing can enhance learning in a variety of ways. To give just a few examples, frequent testing in classrooms encourages students to study continuously throughout a course, rather than bunching massive study efforts before a few isolated tests (Fitch, Drucker, & Norton, 1951). Tests also give students the opportunity to learn from the feedback they receive about their test performance, especially when that feedback is elaborate and meaningful, as is the case in the technique of formative assessment, discussed in a later section. In addition, if students test themselves periodically while they are studying (as Bacon and James advocated long ago), they may use the outcome of these tests to guide their future study toward the material they have not yet mastered. The facts that testing encourages students to space their studying and gives them feedback about what they know and do not know are good reasons to recommend frequent testing in courses, but they are not the primary reasons we focus on in this article. In these cases of mediated effects of testing, it is not the act of taking the test itself that influences learning, but rather the fact that testing promotes learning via some other process or processes. For example, when a test provides feedback about whether or not students know particular items and the students guide their future study efforts accordingly, testing promotes learning by making later studying or encoding more effective; thus, testing enhances learning by means of this mediating process. These examples of mediated effects of testing serve as additional evidence in favor of the use of frequent testing in education. However, our review is focused on direct effects of testing on learning—the finding that the act of taking a test itself often enhances learning and long-term retention. In many of the experiments we describe, one group of students studied some set of materials and then was given an initial test (or sometimes repeated tests). Retention of the material was assessed on a final criterial test, and the tested group’s performance was compared with that of one or two control groups. In one type of control, students studied the material and took the final test just as the tested group did, but were not given an initial test. In a second type of control (a restudy control), students studied the material just as the tested group did, but then studied the material a second time when the tested group received the initial test; in this case, total exposure time to the material was equated for the tested and control groups. The typical finding throughout the literature is that the tested group outperforms both kinds of control groups (the no-test control and the restudy control) on the final test, even when no feedback is given after the initial test. In variations on this prototypical experiment, the effects of several variables have been investigated (e.g., the materials to be learned, the format of the initial and final tests, whether or not subjects receive feedback on the first test, the time interval between studying and initial testing, and the retention interval before the final test, to name but a few). As we show, across a wide variety of contexts, the testing effect remains a robust phenomenon. The direct effects of testing are especially surprising when exposure time is equated in the tested and study conditions, because although the repeated-study group experiences the entire set of materials multiple times, the students in the tested group can experience on the test only what they are able to produce, at least when the test involves recall. Yet despite the differences in initial exposure favoring the study group, the tested group performs better in the long term. That the testing effect is so counterintuitive helps explain why it remains unknown in education. The direct effects of testing on learning are not purely a result of additional exposure to the material, which indicates that processes other than additional studying are responsible for them. The testing effect represents a conundrum, a small version of the Heisenberg uncertainty principle in psychology: Just as measuring the position of an electron changes that position, so the act of retrieving information from memory changes the mnemonic representation underlying retrieval— and enhances later retention of the tested information. In this article, we review research from both experimental and educational psychology that provides strong evidence for the direct effect of testing in promoting learning. After presenting two classic studies, we consider evidence from laboratories of experimental psychologists who have investigated the testing effect. As is the experimentalists’ predilection, they have typically used word lists as materials, college students as subjects, and standard laboratory tasks such as free recall and pairedassociate learning (see Cooper & Monk, 1976; Richardson, 1985; and Dempster, 1996, 1997, for earlier and somewhat more focused reviews). Effects on later retention are usually quite large and reliable. We next consider studies conducted in more educationally relevant situations. Such studies often use prose passages about science, history, or other topics as the subject matter and investigate the effects of tests more like those found in educational settings (e.g., essay, short-answer, and multiplechoice tests). Once again, we show that testing promotes strong positive effects on long-term retention. We also review studies carried out in actual classrooms using even more complex materials, and they again show positive effects of testing on learning. After concluding our review of basic research findings, we provide an overview of theoretical approaches that have been directed toward explaining the testing effect, although many puzzles about testing have not been satisfactorily explained. We then consider the related approaches of dynamic testing (e.g., Sternberg & Grigorenko, 2002) and formative assessment (e.g., Black & Wiliam, 1998a), which are both aimed at using tests to promote learning by altering instructional techniques on the basis of the results of tests (i.e., mediated effects of testing). Because testing does not always have positive consequences, we next review two possible negative effects (retrieval interference and negative suggestibility) that need to be considered when using tests as possible learning devices. Finally, we discuss 182 Volume 1—Number 3 The Power of Testing Memory at Harvard Libraries on July 13, 2010 pps.sagepub.com Downloaded from common objections to increased use of testing in the classroom, and we tell why we believe that none of these objections outweighs our recommendations for frequent testing.