FORUM ON EDUCATION
August 1995

Book Review

A Guide to Introductory Physics Teaching,

by Randy Knight

Arnold Arons must have felt, for many years, like an Old Testament prophet crying in the wilderness. For more than twenty years, Arons has been studying how students really learn physics, in stark contrast to how most of us assume they do or think they should. He has tried, in an outpouring of articles in the American Journal of Physics, The Physics Teacher, and elsewhere, to get our attention. His efforts, and those of a small group of like-minded colleagues, are beginning to bear fruit as the field of physics education research grows in stature.

This book is a masterful compilation of what Arons, and others, have learned about the learning of physics. It presents powerful and insightful suggestions about using this information to change and improve the teaching of physics. Blended throughout are Arons' knowledgeable views on the history of science, the role of language, and the importance of critical thinking. It is seasoned liberally with his dry wit and personal vision. Every teacher of introductory physics, from high school through the calculus-based course, should have a copy of this book within easy reach.

Anyone who has taught introductory physics is all too familiar with the student who can work all of the end-of-chapter problems but is completely stymied by even the simplest request to "explain" an observation. More distressing are the great number of students who, despite high SAT scores and impressive high school credentials, flounder hopelessly in physics and "just don't get it." For those of us who have spent years assimilating the concepts of physics, until they seem clear and obvious, it is extremely difficult to remember just how difficult, abstract, and non-intuitive these concepts really are. The fact that it took scientists the stature of Galileo, Newton, and Faraday to recognize the fundamental ideas and concepts of physics, while most of their contemporaries "just didn't get it," should remind us of this. Perhaps, just perhaps, a nine-month forced march through an enormous body of material is not an effective means for teaching, or learning, what is important about physics.

Arons' contribution to education has been to learn, via direct interviews and the analysis of carefully constructed questions, what students are thinking of and about as they work problems, watch demonstrations, or attempt to reason about a physical situation. He, and his colleagues who have made significant contributions to this research, have discovered a wide range of thought patterns and reasoning strategies that are used by students in introductory physics. Their findings, it should be noted, have been widely replicated by many researchers using students at many different universities. The results are as robust and reproducible as the results of any physics experiment.

Many of what we, as teachers, call "misconceptions" of our students are more correctly identified as "preconceptions" or "prior conceptions." Much instruction, and instructional material, is based on the tacit assumption that students are empty vessels, tabula rasa, waiting to be filled with the correct knowledge of physics. But, in reality, students have spent 18 or so years of their lives before they reach our classrooms as "experimental physicists," forming their own "theories" to correlate and explain their experiences in the physical world. These prior conceptions are not well articulated, or even consciously recognized, by students, and they often contain what, to us, seem blatant logical inconsistencies. Yet these naive theories underlie our "common sense" views about the world, and many correspond closely to physical theories held by the wisest pre-Newtonian scientists. They have been extremely successful in allowing the theory holder to get through life and to make sense of his or her experience.

Examples of such prior conception are that a force is needed to sustain motion (which implies that force is proportional to velocity rather than to acceleration), that objects in space are "weightless" because there is no gravity there, that batteries are sources of constant current, and that the current is "used up" by circuit elements such as light bulbs. These prior conceptions, and many others that Arons describes, are extremely robust and resistant to change. They do not vanish just because we announce the "correct theory" to students. Neither, it has been shown, do standard demonstrations or laboratory experiments have much success at changing students' concepts. The student who can solve the problems but not give an explanation has partitioned his mind into "knowledge for solving physics problems" and his still unaltered "knowledge about how the world really is." As unwelcome as this news is, Arons provides extensive documentation as to its pervasiveness.

These underlying, prior conceptions are not recognized, or are quickly glossed over, by traditional texts and teaching methods. Arons contends, and he marshals an impressive array of evidence to bolster his assertion, that these prior conceptions must be explicitly unearthed and confronted head-on before students can succeed in physics. His objective with this book, he states, "is to bring out as clearly and explicitly as possible the conceptual and reasoning difficulties many students encounter and to point up aspects of logical structure and development that may not be handled clearly or well in substantial segments of textbook literature."

Arons presents a strong case that we, as teachers, have a lot to learn about learning. But his book is far more than an academic analysis of the problem. It is, in addition, very much a presentation of specific and practical ideas for how to teach physics more effectively. It is, you might say, a guide for how to be a teacher rather than just a lecturer. Roughly half the book is devoted to Newtonian mechanics, and most of the rest to electricity, magnetism, circuits, and waves. There is a short section on early modern physics, while other topics, such as thermal physics, are mentioned only in passing. This uneven coverage is understandable, since research into the nature of student learning difficulties has focused most heavily on mechanics. Even so, the reader is sometimes left wishing for a more balanced treatment.

The book provides extensive suggestions for presenting material in novel ways, for filling in the many logical gaps that trip up students (and which we, through familiarity, rarely see at all), and for activities and demonstrations that engage students in active learning. Arons stresses the importance of multiple representations of knowledge through graphs, pictures, free body diagrams, and so forth, but he cautions that students need explicit instruction and much practice before these become useful tools. He notes, in conjunction with free body diagrams, "It is a well-known phenomenon that many students, when they first start drawing free body diagrams, produce pictures resembling a porcupine shot by an Indian hunting party."

While students can learn to make very successful use of free body diagrams and other thinking tools, they need instruction and repeated practice to do so. Since traditional texts offer little or no appropriate practice opportunities, Arons provides an extensive sample of supplemental homework and exam problems focused on these issues. This is one of the major strengths of the book. These are, he notes, not intended to replace more traditional quantitative problems but, instead, "to confront the mind of the learner with aspects otherwise not being made explicit."

Arons' perspective on the teaching, and learning, of physics is summed up in two questions he insists we pose, over and over, to students: "How do we know ...? Why do we believe ... ?" This is, after all, the essence of understanding physics as a science, a way of knowing, rather than as a collection of loosely related formulas. Perhaps, just perhaps, there really is a hope that science education, and physics education in particular, can be improved if Arnold Arons just keeps prodding us along.

Randy Knight is Professor of Physics at California Polytechnic State University in San Luis Obispo. He is developing new curriculum materials based on physics education research.