Download Analogies in science and science teaching

Adv Physiol Educ 34: 167–169, 2010;
doi:10.1152/advan.00022.2010.
A Personal View
Analogies in science and science teaching
Simon Brown and Susan Salter
School of Human Life Sciences, University of Tasmania, Tasmania, Australia
Submitted 8 February 2010; accepted in final form 26 September 2010
analogy; misconception; structure-mapping theory
“And, remember, do not neglect vague analogies. Yet, if you
wish them respectable, try to clarify them.”
George Polya (24), mathematician and teacher.
IN DAILY LIFE, we encounter metaphors and analogies very
frequently (13), but it appears that they are often misunderstood or discounted (6, 16). In contrast, analogies are used in
science to develop insights into, hypotheses and questions
about, and explanations of phenomena that are usually unobservable: they must be understood. In science, two systems are
analogous if they agree in the relations between their respective
parts (the meaning of “relations” and “parts” below). It has
often been asserted that they are fundamental to the development of new ideas (10, 24). Hofstader (15) argues that analogy
is “ . . . the lifeblood . . . of human thinking.” The important
role of analogy has been demonstrated by many examples in
the history of science (19).
Given this tension between the frequency of use and the
chance of a lack of comprehension, it is inevitable that both
metaphors and analogies are used in teaching science and that
they are often regarded with concern because they can engender “misconceptions” (23, 28) that can be difficult to identify
(3, 21) and rectify (5, 26). For some, such is the strength of this
concern that they suggest that “analogies should never be used
as arguments to reach a conclusion” and that “they encourage
lazy and sloppy habits of thought” (27).
We use metaphors and analogies so often that we may not
need to think about what we are doing and may not appreciate
fully the extent to which our students fail to understand what is
being done. Genevie and Cooper (6) informally reported on
experiments with mock juries, and their results prompted the
inference that Lord Justice Greer’s “man on the Clapham
omnibus” [Hall vs. Brooklands Auto-Racing Club (1933)] is
Address for reprint requests and other correspondence: S. Brown, School of
Human Life Sciences, Univ. of Tasmania, Locked Bag 1320, Launceston,
Tasmania 7250, Australia (e-mail: [email protected]).
not necessarily adept at understanding analogies and may often
ignore them. Perhaps, as Treagust et al. (29) suggested, “to
emulate the analogical reasoning of scientists and philosophers
may be too much to expect of unsophisticated thinkers,”
although no tertiary student ought to remain an “unsophisticated” thinker for long.
Science students have to be exposed to analogical reasoning
to understand the nature and common arguments of science,
even for those sharing Simanek’s (27) view, because they will
encounter them frequently. Moreover, it is inevitable that
students will enter our classes with conceptions that conflict to
differing extents with our own, if only because science develops so quickly. These differing conceptions of science are
interesting “because they reveal a thought process and, by
contrast, shed light on some structural features of accepted
theory” (30). Analogies provide an opportunity to teach about
science as well as teaching science, but they have to be
explicitly acknowledged.
If this is the case, then students have to be taught about
analogy, just as they are routinely taught about other forms of
figurative language, specific elements of which often have to
be explained or taught because they are not obvious from the
words used (14). A frequently cited example is the phrase
“kick the bucket,” which may be interpreted literally but also
has a figurative meaning that is not apparent from any of the
constituent words. One must know both interpretations and
decide which of them is appropriate in order for communication to be effected. Similarly, one must understand the elements of an analogy to be able to decide what is intended by it.
Several strategies can help to overcome the problem:
1. Teach the students about analogy (12, 18, 20)
2. Take care to develop good analogies (22, 23)
3. Explicitly explain the structure of the analogy and its
limitations (12)
4. Where appropriate, use more than one analogy (11, 28)
Of these, perhaps only the first is arguably less commonly
observed in classrooms and lecture theatres, but it is critical if
student and teacher do not share a common understanding of
analogy.
Characteristics of Analogy
Analogy is a specific form of similarity, but it is often quite
vague (24). Few of the analogies used in science are as
straightforward as the simplest analogy (such as “an arm is to
a leg as a hand is to a foot”), but Gentner’s (8) structuremapping theory is helpful in understanding the nature of more
complex analogies and in clarifying specific examples. According to this model, an analogy is a mapping of knowledge
from one domain (the base) onto another (the target). The
objects that make up the base have specific attributes and are
linked by a system of relations, which also holds in the target
(Fig. 1). The strength of an analogy depends on the interdomain consistency of the relations rather than the attributes (8,
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Brown S, Salter S. Analogies in science and science teaching. Adv
Physiol Educ 34: 167–169, 2010; doi:10.1152/advan.00022.2010.—
Analogies are often used in science, but students may not appreciate
their significance, and so the analogies can be misunderstood or
discounted. For this reason, educationalists often express concern
about the use of analogies in teaching. Given the important place of
analogies in the discourse of science, it is necessary that students are
explicitly shown how they work, perhaps based on the structuremapping theory we outline here. When using an analogy, the teacher
should very clearly specify both its components and its limitations.
Great care is required in developing an analogy to ensure that it is
understood as intended and that misconceptions are minimized. This
approach models the behavior of a scientist, which helps to develop
student understanding of the practice of science.
A Personal View
168
ANALOGIES
applied to areas ranging from enzyme catalysis (1) and cell
biology (2) to the global ecosystem (17). While the machine
analogy is valuable, it can lead to confusion. For example, the
heart is often compared with a pair of linked pumps, but a
student might have no conception of how a pump works or,
perhaps worse, might visualize any one of many different sorts
of pump. Even if the heart/pump analogy can be well defined
and all the features of the heart accommodated, is the same sort
of pump to be envisaged when considering the “Na⫹-K⫹
pump” or “Ca2⫹ pump?”
Teach Students About Analogy
24). In those cases where the base and target have common
attributes [consider an analogy between (hand, glove) and
(foot, shoe)] and common relations (such as “is covered by,” so
a hand is covered by a glove and a foot is covered by a shoe),
there is similarity (Fig. 1). Where base and target have common attributes but do not share relations, there is just a
superficial similarity (consider the relation “is protected by,” so
a foot is protected by a shoe, but a glove provides little
protection for a hand). Analogy arises where the base and
target do not have common attributes [like (hand, glove) and
(key, lock)] but do share relations [the relation “fits perfectly”
can be applied to both (hand, glove) and (key, lock)]. In most
analogies, some relations do apply to both the base and
target, but others do not. Useful analogies have larger numbers of shared relations and small numbers of common
attributes (Fig. 1).
For example, water flowing through a pipe is often used as
an analogy for blood flowing in a blood vessel (25). Assuming
that the comparison is taken beyond the “a blood vessel is a
pipe” metaphor, the objects in the base are (water, pipe), and a
relation between them might be the flow, which depends on
both the viscosity of the water and the diameter of the pipe
(which are attributes of the corresponding objects). The objects
in the target are (blood, blood vessel), and, again, the flow of
blood depends on the viscosity of blood and the diameter of the
vessel. However, like all analogies, the (water, pipe) ¡ (blood,
blood vessel) analogy does not completely map all of the
relevant relations of the target concept. For example, elasticity
is an important attribute of blood vessels but not necessarily of
the sorts of pipe a student might visualize (28), leading to
misconceptions about the behavior of blood vessels. Similarly,
blood and water differ in their mechanical properties (water is
a Newtonian fluid, whereas blood is not), which means that
they respond differently to changes in conditions, which is
important for blood as it passes through capillaries, for example.
Many important physiological analogies are related to the
suggestion that the human body is analogous to a machine,
usually attributed to Descartes in Traité de l’Homme, although
mechanical analogies for physiological processes were used
before its publication in 1633. The machine analogy is often
While analogies are frequently encountered in daily life
(13), there is no compelling justification for assuming that
students will necessarily understand how they work (16), and
so this should be made clear. Even if students are familiar with
metaphor and analogy, they may not connect this insight with
the examples they subsequently meet in the science classroom.
It is, therefore, only reasonable to teach students about the
nature of analogy. This has been an effective strategy in
various contexts (9, 12, 18, 29).
At least three questions are prompted by the intention to
teach about analogy: 1) what is an analogy, 2) what are
analogies used for (and what are the advantages of this), and
3) what are the limitations of analogy? Defining analogy for
students need not involve explicitly teaching the Gentner
model or an alternative, but it is important to distinguish the
concepts of relation and attribute. For example, Gionfriddo (9)
described a simple model involving red and green apples and
a green pear, in which she asked students to decide how the
fruits could be grouped (by color or type of fruit, for example).
The role of analogy in making a complex concept more
accessible and the limitations of analogy in this respect can be
taught by example.
Explain Analogies Clearly: Mappings, Significance(s),
and Limitations
A significant risk of the use of analogy is that the student is
left with ill-defined ideas unless the teacher explains the
analogy. While it is clearly the case that analogy can be vague,
the “vagueness of analogy need not diminish its interest and
usefulness” (24). Nevertheless, it is inevitable that an analogy
will fail, if only because, were all the relations in the target
concept to map to the base concept, then there would simple
identity (Fig. 1). Polya’s dictum (24) that if we are to make
analogies respectable, we should clarify them is apposite.
Clarification of an analogy involves clearly comparing the
base and target but, more importantly, demonstrating the relations that they share and those that are not shared. In the (water,
pipe) ¡ (blood, blood vessel) example, the shared relations
and attributes are easily stated (as they are above), but the
limitations of the analogy (such as those previously outlined)
are critical to a sophisticated appreciation of the flow of blood
through a vessel. In this example, as in many others, analyzing
the limitations of the analogy enables one to teach more
effectively. Moreover, the analysis of such limitations teaches
students about the nature of science, not only about the example being considered. Arguably, this latter benefit is fundamentally important: analogies are much more than just teaching
tools; they are also tools for developing ideas, insights, and
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Fig. 1. The similarity space indicating the sharing of relations and attributes
between the base and target domains. If the base and target share attributes but
not relations, their similarity is superficial; if they share both relations and
attributes, they are literally similar (or perhaps even identical). In an analogy,
the relations are shared between the base and target, but the attributes are not.
[From Gentner (7).]
A Personal View
ANALOGIES
Develop Good Analogies Carefully
Good analogies are simple, easy to remember, and based on
familiar analog concepts (23). The (water, pipe) ¡ (blood,
blood vessel) example satisfies these requirements, but even
such good analogies have limitations, as outlined above. Orgill
and Bodner (23) recommended that analogies should be used
when a difficult or challenging concept that cannot be visualized is introduced. However, they warn against the use of
analogy when the target concept is overwhelming or has to be
memorized. To be most effective, the elements of an analogy
must be made clear and its limitations need to be explained.
Conclusions
Much of the education literature concerning analogy relates
to events in pretertiary classrooms, where the students may not
be sophisticated enough to appreciate the nuances of scientific
thought (29), but in tertiary classrooms, students need to
understand the nature of science, the modes of argument, and
model construction. If we give in to Simanek’s (27) view,
students may learn the “facts” but not the “thought” that led to
them. Arguably, the thought is more significant than the facts,
which can be learned and are rapidly forgotten (4). So, students
should be taught about argument, analogy, induction, and the
other skills of logic that are commonly used in science. In other
words, we should teach not only science but also about science.
DISCLOSURES
No conflicts of interest, financial or otherwise, are declared by the author(s).
REFERENCES
1. Brown S. Developing the enzyme-machine analogy: a non-mathematical
approach to teaching Michaelis-Menten kinetics. Orbital 2: 92–100, 2010.
2. Cardoso FS, Dumpel R, da Silva LBG, Rodrigues CR, Santos DO,
Cabral LM, Castro HC. Just working with the cellular machine. A high
school game for teaching molecular biology. Biochem Mol Biol Educ 36:
120 –124, 2008.
3. Clerk D, Rutherford M. Language as a confounding variable in the
diagnosis of misconceptions. Int J Sci Educ 22: 703–717, 2000.
4. Custers EJFM. Long-term retention of basic science knowledge: a review
study. Adv Health Sci Educ 15: 109 –128, 2010.
5. Feltovich PJ, Coulson RL, Spiro RJ, Adami JF. Conceptual Understanding and Stability, and Knowledge Shields for Fending Off Conceptual Change. Springfield, IL: Southern Illinois Univ. School of Medicine,
1994.
6. Genevie L, Cooper D. Why analogies often fail. For the Defense: and
4322–23, 2001.
7. Gentner D. The mechanisms of analogical learning. In: Similarity and
Analogical Reasoning, edited by Vosniadou S, Ortony A. Cambridge:
Cambridge Univ. Press, 1989, p. 199 –241.
8. Gentner D. Structure-mapping: a theoretical framework for analogy.
Cognitive Sci 7: 155–170, 1983.
9. Gionfriddo JK. Using fruit to teach analogy. Second Draft 12: 4 –5, 1997.
10. Hadamard J. An Essay on the Psychology of Invention in the Mathematical Field. New York: Dover, 1945.
11. Harrison AG, De Jong O. Exploring the use of multiple analogical
models when teaching and learning chemical equilibrium. J Res Sci Teach
42: 1135–1159, 2005.
12. Harrison AG, Treagust DF. Teaching with analogies: a case study in
grade-10 optics. J Res Sci Teach 30: 1291–1307, 1993.
13. Hoffman RR. Recent research on metaphor. Semiotic Inquiry 3: 35– 62,
1983.
14. Hoffman RR, Honeck RP. Proverbs, pragmatics, and the ecology of
abstract categories. In: Cognition and Symbolic Structures: the Psychology
of Metaphoric Transformation, edited by Haskell RE. Norwood, NJ:
Ablex, 1987, p. 121–35–140.
15. Hofstader DR. Analogy as the core of cognition. In: The Analogical
Mind: Perspectives From Cognitive Science, edited by Gentner D, Holyoak KJ, Kokinov BN. Cambridge, MA: The MIT Press, 2001, p.
499 –538.
16. Hunter D. Teaching and using analogy in law. J Assoc Legal Writing
Directors 2: 151–168, 2004.
17. Hutton J. Theory of the Earth. Trans R Soc Edinburgh 1: 209 –304, 1788.
18. Klauer KJ. Teaching for analogical transfer as a means of improving
problem-solving, thinking and learning. Instruct Sci 18: 179 –192, 1989.
19. Mach E. Erkenntnis und Irrtum. Skizzen zur Psychologie der Forschung.
Leipzig: Johan Ambrosius Barth, 1905.
20. Mason L. Cognitive and metacognitive aspects in conceptual change by
analogy. Instruct Sci 22: 157–187, 1994.
21. Morrison JA, Lederman NG. Science teachers’ diagnosis and understanding of students’ preconceptions. Sci Educ 87: 849 – 867, 2003.
22. Orgill MK, Bodner G. Locks and keys. An analysis of biochemistry
students’ use of analogies. Biochem Mol Biol Educ 35: 244 –254, 2007.
23. Orgill MK, Bodner G. What research tells us about using analogies to
teach chemistry. Chem Educ Res Pract 5: 15–32, 2004.
24. Polya G. Mathematics and Plausible Reasoning. I. Induction and Analogy
in Mathematics. Princeton, NJ: Princeton Univ. Press, 1954.
25. Pontiga F, Gaytán SP. An experimental approach to the fundamental
principles of hemodynamics. Adv Physiol Educ 29: 165–171, 2005.
26. Posner GJ, Strike KA, Hewson PW, Gertzog WA. Accomodation of a
scientific conception: toward a theory of conceptual change. Sci Educ 66:
211–227, 1982.
27. Simanek DE. The Dangers of Analogies (online). http://www.lhup.edu/
⬃dsimanek/scenario/analogy.htm [29 September 2010].
28. Spiro RJ, Feltovich PJ, Coulson RL, Anderson DK. Multiple analogies
for analogy-induced misconception in advanced knowledge acquisition.
In: Similarity and Analogical Reasoning, edited by Vosniadou S, Ortony
A. Cambridge, MA: Cambridge Univ. Press, 1989, p. 498 –531.
29. Treagust DF, Harrison AG, Venville GJ. Using an analogical teaching
approach to engender conceptual change. Int J Sci Educ 18: 213–229,
1996.
30. Viennot L. Reasoning in Physics. The Part of Common Sense. New York:
Kluwer Academic, 2001.
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hypotheses. The exploration of an analogy compared with the
results of experimental exploration of the phenomenon it models helps to identify misconceptions. Analogy is a tool of
science, and its use is, in effect, a model of professional
behavior.
Many concepts can be expressed mathematically, for example, blood flow through a blood vessel can be expressed in
mathematical form (25). The equations constituting such a
mathematical model are themselves an analogy of the phenomenon to which they relate. The mathematical variables represent particular real-world observables, and the relationships
between those observables are expressed by the mathematical
functions in the equations. For example, returning to the
(water, pipe) ¡ (blood, blood vessel) analogy, a standard
mathematical application of Poiseuille’s law relates the pressure drop (⌬p) to the volume flow rate (Q) using the diameter
(D) and length (L) of the vessel and the viscosity (␩) of the
blood (25). In this case, the analogy embodied in the mathematical model could be written as (⌬p, Q, D, L, ␩) ¡ (pressure
drop, flow rate, diameter, length, viscosity). As with nonmathematical analogies, a vital function of a mathematical model is
testing an ability to predict real-world events and to identify
misconceptions.
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