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Appendix B Reference Paper
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Improving Student Learning in Science Through Discipline-Based Education Research Lillian C. McDermott Department of Physics, University of Washington INTRODUCTION I would like to thank the Council of Scientific Society Presidents for the 2000 Award for Achievement in Educational Research. The accomplishments recognized by this honor are the result of many contributions by faculty, postdocs, graduate students, K–12 teachers, and undergraduates in the Physics Education Group at the University of Washington. Perhaps my “most seminal research achievement” has been to demonstrate, in the context of physics, the value of discipline-based education research. This type of research differs from traditional education research in that the emphasis is not on educational theory or methodology in the general sense but rather on student understanding of science content. For both intellectual and practical reasons, discipline-based education research must be conducted by science faculty within science departments. I shall present some evidence that this is an effective approach for improving student learning (K–20). The emphasis here will be on introductory university students and K–12 teachers. CONTEXT FOR RESEARCH A brief description of the Physics Education Group can set a context for our research. Our group is an entity within the Physics Department in the same sense that there are groups in other subfields of physics. The courses in the department provide the primary environment for our investigations. Most of our work involves two populations: undergraduates in the introductory calculus-based course and prospective and practicing K–12 teachers who are taking special courses designed to
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prepare them to teach physics and physical science by inquiry. Our investigations also include students in engineering and in advanced undergraduate and graduate physics courses. As part of our research on how to improve student learning in physics, we try to identify specific difficulties that students encounter in the study of various topics. The results are used to design instructional materials that target these difficulties and help guide students through the reasoning required to overcome them and to develop a coherent conceptual framework. Assessment of effectiveness with students is an integral part of the iterative process through which the Physics Education Group develops curriculum. To ensure applicability beyond our own university, our materials are also tested at pilot sites (e.g., Georgetown, Harvard, Illinois, Maryland, Purdue). Our two major curriculum projects are Physics by Inquiry (McDermott, Shaffer, and Rosenquist, 1996) and Tutorials in Introductory Physics (McDermott, Shaffer, and the Physics Education Group, 1998). The development of both is guided by research. The first is a self-contained, laboratory-based curriculum for the preparation of K–12 teachers; the second is a supplementary curriculum that can be used in conjunction with any standard text. PERSPECTIVE ON TEACHING AS A SCIENCE The perspective that teaching is a science, as well as an art, motivates our work. Considered as a science, teaching is an appropriate field for scholarly inquiry by scientists. This view is in marked contrast to that held by many science faculty. A more traditional view was expressed in 1933 in the first article in the first journal published by the American Association of Physics Teachers (AAPT). In “Physics is Physics,” F.K. Richtmyer (Cornell University) argued that teaching is an art and not a science. He quoted R.A. Millikan (California Institute of Technology) in characterizing science as comprising “a body of factual knowledge accepted as correct by all workers in the field.” Richtmyer went on to say: “Without a reasonable foundation of accepted fact, no subject can lay claim to the appellation ‘science.’ If this definition of a science be accepted—and it seems to me very sound—then I believe that one must admit that in no sense can teaching be considered a science.” Although this is a somewhat limited definition of science, I would like to challenge the implication that it is not possible to build “a reasonable foundation of accepted fact” for the teaching of physics (and, by extension, other
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sciences). For example, we have found that most people encounter many of the same conceptual and reasoning difficulties in learning a given body of material. These difficulties can be identified, analyzed, and effectively addressed through an iterative process of research, curriculum development, and instruction. Both the learning difficulties of students and effective means for addressing them are often generalizable beyond a particular course, instructor, or institution. If one documents intellectual outcomes for student learning, teaching can be treated as a science. If the criteria for success are clearly stated and the results are reproducible, findings from research can contribute to “a reasonable foundation of accepted fact.” This foundation is represented by a rapidly growing research base. The personal qualities and style of an instructor contribute to the aspect of teaching that can be viewed as an art (a benefit confined to the instructor’s class). However, when student learning is used as the criterion (as distinct from student enthusiasm), we have found that effective teaching is not as tightly linked as is often assumed either to self-assessment of learning by students or to their evaluation of the course or instructor. FOCUS ON THE STUDENT AS A LEARNER The focus of our research is on the student as a learner, rather than on the instructor as a teacher. We try to determine the intellectual state of the student throughout the process of instruction. To the degree possible, we try to follow the procedures and rules of evidence of an experimental science. We conduct our investigations in a systematic manner and record our procedures so that they can be replicated. We use two general methods: individual demonstration interviews (which allow deep probing into the nature of student difficulties) and written tests (which provide information on prevalence). Continuous pre-testing and post-testing enable us to judge the effectiveness of instruction. Although experienced instructors know there is a gap between what they say and what students learn, most do not recognize how large the gap can be. The usual means of evaluation in physics courses—the ability to solve standard quantitative problems—is not adequate as a criterion for a functional understanding and unfortunately reinforces the perception of physics as a collection of facts and formulas. Success on numerical problems does not provide adequate feedback for improving instruction. Questions that require
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qualitative reasoning and verbal explanations are essential. Our investigations have shown that on certain types of qualitative questions, student performance in physics is essentially the same: before and after standard instruction by lecture and textbook, in algebra-based and calculus-based courses, whether or not there is a standard laboratory, whether or not demonstrations are used, whether classes are large or small, and regardless of the proficiency of the instructor as a lecturer. The situation has been the same in introductory mechanics, electricity, magnetism, waves, optics, and thermodynamics. We have also found that advanced students often have difficulty with qualitative questions on introductory physics, as well as on topics such as special relativity and quantum mechanics. There is by now ample evidence that teaching by telling is ineffective for most students. They must be intellectually active to develop a functional understanding. The instructor of a course determines the emphasis, motivates students, and can promote a view of science as a human endeavor. However, he or she cannot do the thinking for the students. They must do it for themselves. Some are reluctant to do so; others do not know how. SCIENCE COURSES FOR INTRODUCTORY STUDENTS Introductory science courses should help students construct basic concepts, integrate them into a coherent conceptual framework, and develop the reasoning ability necessary to apply them in situations not explicitly memorized. Significant progress toward these goals is not usually made in a traditional course. In particular, scientific reasoning skills must be expressly cultivated. Physics instructors present lectures that include detailed derivations, lucid explanations, and suitable demonstrations. However, they often proceed from where they are now and do not remember where they were (or think they were) as students. They frequently think of students as younger versions of themselves. This approach is not well matched to an introductory class since fewer than 5 percent of the students will major in physics. (The percentages in chemistry and biology are a little higher.) Meaningful learning requires active mental engagement. The challenge, especially in large courses, is how to achieve the necessary degree of intellectual involvement. Much of our research has been directed toward responding to that challenge in ways that are effective not only at our own university but in other instructional
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settings as well. We are developing Tutorials in Introductory Physics to engage students actively in learning physics. SCIENCE COURSES FOR K–12 TEACHERS Science departments have a major responsibility for the education of K–12 teachers, both prospective and practicing. Many science faculty assume that this is a role solely for education faculty. In fact, the only place that the subject matter preparation of teachers can occur is in science courses. The study of educational psychology and methodology cannot help teachers develop the depth of understanding of science content that they need in order to teach effectively. The national effort to improve K–12 science education will not succeed without the direct involvement of science faculty. The courses offered by most science departments do not provide adequate preparation for K–12 teachers. Descriptive courses are useless for preparing elementary and middle school teachers to help students learn basic concepts and reasoning skills. High school teachers are not adequately prepared by mainstream courses, including the sequence for majors. For example, the traditional introductory physics course and (to an even greater extent) upper division physics courses emphasize mathematical formalism. The breadth of topics covered allows little time for acquiring a sound grasp of the underlying concepts. In addition to deficiencies in subject matter preparation, traditional science courses have another major shortcoming. Teachers tend to teach as they were taught. If taught through lectures, they are likely to teach that way. Moreover, this type of instruction is unlikely to lead to an understanding of the nature of science and thus does not help prepare teachers to teach science as a process of inquiry. Teachers need to learn (or relearn) science in a way that is consistent with how they are expected to teach. For more than 25 years, our group has provided that opportunity through special physics courses for prospective and practicing K–12 teachers. These classes have provided an environment for research on the preparation needed for teaching physics and physical science by inquiry. The results have guided the development of Physics by Inquiry. RESEARCH AS A GUIDE FOR CURRICULUM DEVELOPMENT: AN EXAMPLE Research guides the development of all curricula. The topics in Tutorials in
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Introductory Physics respond to the questions: Is the standard presentation in textbook and lecture adequate to develop a functional understanding? If not, what can be done? The illustrative example below is discussed more fully in two published articles (Wosilait et al., 1998; Heron and McDermott, 1998.) In teaching geometrical optics, most instructors begin with the premise that university students have a functional understanding of the rectilinear propagation of light. Virtually all students can state that “light travels in straight lines” and many can elaborate that “light travels outward from every point on an object in straight lines.” To determine whether students can apply these concepts in a simple situation, we designed a written question. Pretest Students were asked to predict the image formed on a screen by various light sources located in front of a small aperture in a mask. This question has been given as a pretest to thousands of introductory physics students and to more than 100 teaching assistants in our physics Ph.D. program. The question is called a “pretest” because it usually precedes the tutorial that we developed to address the difficulties that the responses of students revealed. (The question is actually a post-test in that students have already had the relevant material in their university course or K– 12 education.) One part of the question involves a long-filament bulb, a mask with a small triangular hole (~ 1 cm), and a screen. (See Figure B-1.) For a correct response, students must recognize that light travels in straight lines and that a line source can be treated as a series of point sources. The image can be found by treating each point on the bulb as a point source that produces a triangular image on the screen. Since the points are closely spaced, the images overlap substantially. The result is a vertical rectangle terminating at the top in a triangle. Although the amount of prior instruction varied, the results did not. (See Table B-1.) Only about 20 percent of the students answered correctly, either before or after instruction. About 70 precent predicted that the image would be triangular. In this and many other instances, we have found that certain conceptual difficulties are not overcome by traditional instruction. Persistent difficulties must be explicitly addressed. Tutorial The emphasis in the tutorials is on constructing concepts, developing reasoning ability, and relating physics formalism to the real world, not on solving standard quantitative problems. The tutorials are intended for use in a
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FIGURE B-1 Pretest. (a) Students were asked to sketch what they would see on the screen. (b) Correct answer. SOURCE: Wosilait et al. (1998) and Heron and McDermott (1998). Reprinted with permission of the American Association of Physics Teachers and Optical Society of America. small section of about 24 students, in which groups of three or four work together. The structure in these 50-minute sessions is provided by worksheets that guide students through a series of exercises and simple experiments by asking questions. With results from questions like the one described above as a guide, we designed a tutorial entitled Light and Shadow. The tutorial begins by having students predict the images formed by point and line sources with apertures of various sizes and shapes. After making predictions and explaining their reasoning to one another, the students observe what actually happens and try to resolve any discrepancies with their predictions. They are then asked to predict and explain up-down and left-right inversions of images formed by asymmetric sources. These and other exercises help students recognize how the shape and relative size of the source and aperture and the distances involved affect the image. Systematic monitoring in the classroom helped us improve the tutorial. One exercise that was added had a pronounced effect on student understanding of the geometric model for light. The students are asked to predict what they would see on the screen when a frosted light bulb is placed in front of a mask with a triangular hole. Many are surprised to see the inverted image of the bulb. Eventually, they realize that the entire bulb can be
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TABLE B-1 Results from Pretest and Posttest Questions Administered in Introductory Physics Courses and Graduate Teaching Seminars Introductory course Pretests (before tutorial) (N ˜ 1215) Posttests (after tutorial) (N ˜ 360) Graduate seminar Pretests (before tutorial) (N ˜ 110) Correct or nearly correct 20% 80% 65% Incorrect: image mimics shape of hole in mask 70% 10% 30% SOURCE: Wosilait et al. (1998) and Heron and McDermott (1998). Reprinted with permission of the American Association of Physics Teachers and Optical Society of America. considered as a collection of point sources. The students recognize that superposition of the images from the continuum of point sources produces an image that closely resembles the extended source, but is affected by the shape of the aperture. They also note that whether a light source can be treated as a point or extended source depends on a variety of factors. Posttest Throughout the development of the tutorial, assessment played a critical role. In Figure B-2 is one of several posttest questions that we administered on examinations to about 360 students in several introductory courses. The percentage of correct or nearly correct responses was 80 percent, an increase from 20 percent on the pretest. Only 10 percent drew images the same shape as the aperture, in sharp contrast to the 70 percent who made this error on the pretest. (See Table B-1.) The teaching assistants and postdocs who lead the tutorial sessions participate in a weekly graduate teaching seminar in which they work through the pretests and tutorials. About 65 percent have given a correct, or nearly correct, response for the question described above. This result is consistent with our experience that advanced study may not increase student understanding of basic topics. We consider the pretest performance of graduate students to be a reasonable post-test goal for introductory students. As shown in Table B-1, the latter demonstrate a better functional understanding than the graduate students had initially had.
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FIGURE B-2 Posttest question: (a) Students were asked to sketch what they would see on the screen. (b) Correct answer. SOURCE: Wosilait et al. (1998) and Heron and McDermott (1998). Reprinted with permission of the American Association of Physics Teachers and Optical Society of America. COMMENTARY It is tempting for instructors to think that the rectilinear propagation of light is such a simple concept that only a brief discussion of the topic is needed. Evidence to the contrary comes not only from our own research but from the experience of colleagues in our department. Recently, instructors of an honors section and a regular section of the calculus-based course used other approaches to teach this concept. Their students did not work through the tutorial. In the honors section, the instructor demonstrated the image that is formed when light from an object passes through a pinhole. He asked questions to guide the students in explaining what they saw. He assigned homework based on equipment similar to that used in the tutorial. Only about 30 percent of the students responded correctly on the homework. The instructor then distributed solutions. In the regular section, the instructor did not lecture on the propagation of light through an aperture. However, he assigned homework problems that were similar to the instructional sequence in the tutorial. Prompt feedback was given in the form of written solutions. Questions similar to the posttest question in Figure B-2 were posed on midterm examinations in both classes. Only 45 percent of the students in the honors section and 35 percent in the
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regular section gave correct, or nearly correct, responses. Although the time they spent on this material in lecture and on homework was not monitored, we do not believe that this factor alone could account for the large difference in posttest performance between these students and those who had worked through the tutorial. (See Table B-1.) It has been our experience that if instruction does not engage students in confronting and resolving their underlying conceptual and reasoning difficulties, they do not develop the ability to do the reasoning necessary to apply concepts to problems that cannot be solved by memorized formulas. We attribute the success of students who worked through the tutorial to the detailed knowledge of student difficulties that informed its development. The tutorials are a means of engaging students intellectually within the constraints of large, rapidly paced courses. More can be achieved if students can go through similar material more slowly and thoroughly. Teachers who have worked through the development of a ray model for light in Physics by Inquiry can deal successfully with more complicated combinations of light sources and apertures. Research in physics education has shown that the development of a qualitative understanding greatly improves student performance on conceptual problems. Moreover, we and others have found that time spent in this way does not detract from (and often improves) proficiency in solving standard problems. Therefore, increasing the emphasis on qualitative reasoning can help set a higher (yet realistic) standard for student learning. CONCLUSION A major goal of a science course that is likely to be terminal in the discipline is to help students recognize whether or not they understand the basic concepts. In Physics by Inquiry, and to a lesser extent in Tutorials in Introductory Physics, we try to help students learn to answer and to ask the kinds of questions that are necessary to assess and improve their understanding. This ability is critical for all students, but especially for those who plan to teach. Learning to reflect on one’s own thinking transcends the learning of physics or any other science. Our group has demonstrated that, in the context of physics, discipline-based education research can help improve student learning. Recently, there has been a steady increase in the number of physicists who are pursuing this type of research. The results are reported at professional meetings and in articles in refereed journals that are readily acces-
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sible to physics faculty (McDermott and Redish, 1999). Thus, colleagues who are not involved in education research have a rich resource from which to draw in developing print and computer-based instructional materials. Our experience indicates that it is difficult to develop effective curriculum that yields consistent positive results. Therefore, unless faculty can devote a long-term effort to the development and refinement of their own instructional materials, they should take advantage of already existing curriculum that has been carefully designed and thoroughly assessed. Without a research base on student learning, we lack the knowledge necessary to make cumulative progress in improving instruction. There is a need in all the sciences for research on the intellectual development of students as they progress through a given body of material. Investigations of this type demand a depth of understanding that ordinarily is found only among specialists in a field. Therefore, such research must be conducted by science faculty in the context of courses offered by science departments. The American Physical Society has issued a statement in support of research in physics education as a scholarly activity by faculty in physics departments. By taking similar action, other scientific societies could help strengthen efforts to improve student learning in their disciplines. REFERENCES Heron, P.R.L., and McDermott, L.C. (1998). Bridging the gap between teaching and learning in geometrical optics: The role of research. Optics & Photonics News, 9(9), 30–36. McDermott, L.C., and Redish, E.F. (1999). Resource Letter: PER-1: Physics Education Research. American Journal of Physics, 67(9), 755. McDermott, L.C., Shaffer, P.S., and the Physics Education Group. (1998). Tutorials in introductory physics. Upper Saddle River, NJ: Prentice-Hall. McDermott, L.C., Shaffer, P.S., and Rosenquist, M.L. (1996). Physics by inquiry (Vols. I-II). New York: Wiley. Wosilait, K., Heron, P.R.L., Shaffer, P.S., and McDermott, L.C. (1998). Development and assessment of a research-based tutorial on light and shadow. American Journal of Physics, 66(10), 906–913. ACKNOWLEDGMENTS Special thanks are due to the current faculty in the Physics Education Group: Paula R.L. Heron, Peter S. Shaffer, and Stamatis Vokos. In addition to past and present members of our group, I want to express my appreciation to the past and present leadership of the Physics Department and the University of Washington. I would like to recognize the early intellectual influence of Arnold B. Arons and the contributions by our physics colleagues here and elsewhere. I am also grateful to the National Science Foundation for enabling our group to do the research for which this CSSP Award is being given.
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