Book Review
A Guide to Introductory Physics Teaching,
Arnold B. Arons, John
Wiley and Sons (1990), 342 pages.
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.
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