JOURNAL OF RESEARCH IN SCIENCE TEACHING
VOL. 30, NO. 4, PP. 367-380 (1993)
Self-Generated Analogies as a Tool for Constructing and Evaluating
Explanations of Scientific Phenomena
E. David Wong
Department of Teacher Education, 206 Erickson Hall, Michigan State University,
East Lansing, Michigan 48824-1034
Abstract
How can students be taught to develop explanations for scientific phenomena on their own when their
background knowledge is incomplete or poorly organized? Evidence from historical accounts of scientific
discovery suggest that self-generated analogies—analogies produced by the learners themselves—are a
tool by which individuals can generate, evaluate, and modify their own explanations. The central research
questions for this study were: Can students use a series of self-generated analogies to bring about change in
their understanding of a given scientific phenomenon, and what is the nature of the change in
understanding? Participants were asked to create, apply, and modify their own analogies—as opposed to
applying a specific analogy provided by an outsider—as a heuristic for constructing, evaluating, and
modifying their own explanations for a given scientific phenomena. Nontrivial changes in explanation
facilitated by the use of generative analogies were observed. Changes in understanding ranged from the
emergence of new explanations to the raising of important questions about the nature of the phenomenon.
With dramatic flair, the ninth-grade science teacher flourishes the bathroom plunger in front of the class.
Then, in one quick move, he tums and squishes it against the hard surface of the blackboard. The entire
class gasps, then giggles as the plunger remains firmly stuck . . . horizontal.
"Why is this happening?," the teacher asks, motioning to the plunger.
"Suction!" "A vacuum!" are the common responses heard above the clamor of students simultaneously
answering.
"Good thinking!" replies the teacher. "Now, how exactly does a vacuum or suction make the plunger stick
to the surface?"
The class quiets noticeably. After a pause, one student says, "When you push the plunger, a vacuum is
created inside and that makes it stick. You know what I mean?"
The teacher pushes the students a little harder. "Okay. But, why does a vacuum make the plunger stick?"
1993 by the National Association for Research in Science Teaching
Published by John Wiley & Sons, Inc.
CCC 0022-4308/93/040367-12
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The initial enthusiasm subsides even more. Some students are thinking that the question had
already been answered. Others see that the teacher is asking for a deeper explanation, but do not
know how to proceed.
The teacher begins to ask individual students what they think. He is met with "I don't know's,"
shrugged shoulders, or silence.
"It's okay that you don't know," he says brightly to comfort them. "I want you to think of your
own explanation. Push yourselves a little. Make a conjecture like a scientist might!"
No response at all. This is the quietest the class been since he announced the grading scale for the
semester exam. After a long awkward silence, a student in the back, sitting low is his seat with
his arms folded across his chest, speaks loudly—as if for the whole class.
"We said we don't know. Why don't you just tell Us the answer?!"
As this vignette derived from my own teaching experiences illustrates, science students will often find
that moving beyond the boundaries of concrete memorized facts, into the conceptual gray area where
understanding is tenuous and incomplete, is an unfamiliar and uncomfortable experience. Typically,
students are neither expected nor prepared to construct accounts of scientific phenomena on their own.
Instead, they see their role as students to be followers, led carefully by teachers to new and better
understanding. Teachers often share the same view.
When individuals are out in the real world, trying to figure out whether hot or cold air is best to defog a
car window, or striving to design a better space shuttle O-ring, they will often be compelled to move into
that gray area of understanding. To say "I don't know," or to defer to a more knowledgeable authority, is
often not an option considered or available. An important part of a science curriculum, therefore, should
be to develop students' ability to construct their own understanding for scientific phenomena.
The goal of this study was to develop a means by which students could develop, evaluate, and modify
their own explanations for scientific phenomena with minimal subject-specific guidance from the teacher.
The potential of self-generated analogies —where learners use their own analogies as opposed to
analogies provided by a teacher—was explored as a tool for advancing conceptual understanding. In brief,
participants were presented with a scientific phenomenon to explain. When they encountered difficulties
in their explanations, they were asked to construct their own analogies as a means of addressing these
conceptual problems. Instead of receiving an ideal analogy from a more knowledgeable authority,
participants were required not only to create and apply their own analogy, but to also evaluate and modify
the analogy. The central research questions for this study were: (a) Can individuals use a series of
self-generated analogies to bring about change in their understanding of a given scientific phenomenon?
(b) What is the nature of the change in understanding?
Conceptual Background
The process of understanding andproblem solving. In schools, science instruction often follows a
common path: The concepts are taught; the problems are provided; the concepts are used to solve the
problems. The conceptual understanding necessary
SELF-GENERATED ANALOGIES 369
for solving the given problems is assured by prior or concurrent instruction. Furthermore, problems and
the requisite knowledge are presented in close conjunction with each other, making it easier for the
individuals to determine which conceptual knowledge to apply. By contrast, in situations outside of
school, the relationship between a problem and the knowledge appropriate to address it is not as obvious.
In fact, the nature of the problems themselves is often not clear and is strongly influenced by the
individual's prior knowledge and interpretation of the situation. Schon (1979) argues that in human
learning and understanding, the process of probleminding is as central, if not more so, to understanding
than the process of problem solving.
Problem finding is a direct function of conceptual understanding: What one knows affects the types of
problems perceived and the manner in which these problems are construed (cf. Larkin, McDermott,
Simon, & Simon, 1980). This contrasts to typical schoolwork, where identifying problems is either a
nonissue because the problems are stated explicitly, or is a function of understanding task demands. For
example, keeping in mind the most recent topic of instruction is usually a fail-safe strategy for
determining the nature of a problem on a test. Reliance on these types of contextual factors may be one
reason why students often do so poorly on final exams where the nature of problems cannot be as easily
determined by factors unrelated to conceptual understanding.
-The potential of analogies. The rationale for the study is based on the following argument: Because of
the nebulous nature of many problem situations outside of school contexts (especially in contrast to
traditional instructional contexts), students need to develop the ability to identify and represent scientific
phenomena in a manner that enables them to gain a greater understanding on their own. Science
instruction, therefore, should enable students to identify and work on problems with a minimum of
reliance on teacher guidance and instructional cues, and with a maximum emphasis on bringing to bear
their own existing knowledge about the particular phenomenon. In this study, self-generated analogies
were investigated as a tool by which individuals can construct—largely on their own—better accounts of
scientific phenomena. The conceptual argument and design underlying the study was informed by an
examination of analogy use in two different settings: the classroom community and the scientific
community.
Analogies in the classroom. In instructional situations, the analogy is typically constructed by a
knowledgeable individual (teacher) and is used as a means to represent a concept to those who are less
knowledgeable (students). Studies demonstrating or exploring the power of instructional analogies have
varied in their emphasis from using analogies to overcome student misconceptions (Clement, 1987; Spiro,
Feltovich, Coulson, & Anderson, 1989; Stavy, 1991), to analogies as an aid to comprehension and
memory when reading text (Halpem, 1990), to general discussions on the benefits of analogies in
instruction (Duit, 1991; Simons, 1984).
In each of these studies, analogies are provided by an outside authority—the role of the individual is to
make sense of the received analogy. Individuals have minimal responsibility for representing the
scientific phenomenon in their own terms. Although these studies provide important evidence that
analogies do facilitate leaming and understanding, they do not suggest that self-generated analogies might
be of value.
Analogies in the practice of science. The nature of classroom communities— where experts teach
novices—promotes the utility of teacher-provided analogies. Selfgenerated analogies might assume a
more central role in a context where members all see themselves as learners. Such a context exists in the
scientific community, and in d~e practice of science can be found naturally occurring self-generattd
analogies.
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Historical accounts of scientific discovery and insight describe compelling examples of the potential of
analogies (cf. Dreistadt, 1968; Hesse, 1966; Leatherdale, 1974; Nagel, 1974; Oppenheimer, 1956; for
accounts of discovery through analogy in mathematics, see Polva, 1954). The spontaneous and
unpredictable use of analogies makes it difficult to examine the phenomenon as it occurs—most accounts
are based on scientists' retrospective reconstructions of their insights. However, a rare example of a direct
investigation of scientists' use of analogies as a natural part of their work was provided by Schon (1979).
Schon observed researchers at a paintbrush factory as they tried to develop a better paintbrush. During
their brainstorming sessions, significant insights were made through the discovery and application of an
analogy that compared a paintbrush to a pump. Considering the brush as a pumping device, instead of
simply a spreading device, led them to design brush bristles that more effectively hold and squeeze paint
when used. Schon argued that the power of the analogy lies in its ability to lead to a reframing of the
original problem. The altering of the problem space facilitates the emergence of new ideas or solutions
previously unaccessible in the original problem space. Schon contends that it is impossible for new ideas
to arise directly from existing conceptions; only through the altering of some initial assumptions can truly
novel ideas emerge. (Note: Clement's 1988, study of problem-solving methods of physics experts,
although conducted in an artificial setting, also provides examples of spontaneous use of analogies.)
Design of the Task
Although self-generated analogies can occur naturally (as evidenced by scientific discovery), their use is
typically spontaneous and unpredictable. One of the goals for this study was to develop a task that
explicitly encouraged the systematic creation and application of self-generated analogies as a heuristic for
conceptual growth. Theoretical work from psychology and philosophy on analogical reasoning and
problem solving was reviewed to identify processes that would seem likely to promote conceptual growth
(Clement, 1988; Petrie, 1979; Rumelhart & Norman, 1985; Schon, 1979; Vosniadou, 1989). These
processes, upon which the task for this study was based, include
1. Adopt a generative learning perspective: Understanding is viewed as an
iterative,constructive process where the purpose of the task is to develop a plausible
explanation rather than tofind the single correct answer (Vosniadou & Brewer, 1987).
2. Work on a meaningful problem: The starting point is a problem formulated from each
individual's unique understanding of the phenomenon rather than a problem provided and
defined entirely by an outsider (Petrie, 1979; Schon, 1979).
3. Engage in concrete activity with the phenomenon: Sensory activity may stimulate
associations that are not yet possible through abstract, verbal means (Petrie, 1979; Schon,
1979).
4. Generate analogies: Representing the phenomena by relating it to a familiar domain of
knowledge facilitates understanding (Duit, 1990; Simons, 1984).
5. Apply analogies to the phenomenon: Specifying exactly how "A is like B" provides
different perspectives from which one's understanding can be examined and may yield
relationships not recognized when the analogy was first generated (Clement, 1988; Gick
& Holyoak, 1983; Petrie, 1979).
SELF-GENERATED ANALOGIES
371
6. Evaluate the analogies: Any analogy, by definition, suggests inappropriate similarities
that need to be identified (Spiro et al., 1989).
7. Modify existing analogies or generate new analogies: A single analogy is not
commensurate with understanding or the comct explanation. Therefore, the use of
self-generated analogies is a cyclical process of geneMting, evaluating, and modifying.
Methods/Task
Participants. The influence of self-generated analogies on conceptual understanding should, ideally, be
explored for all students of science. Although such a population includes students of all ages, the present
study focused on university students as a starting point for investigation. With the think-aloud
methodology used, these individuals were likely to have a better developed ability to express their thought
processes. Future studies will expand the focus of investigation in two directions: toward younger,
schoolaged students of science, and toward whole-class rather than individual activity.
E]even individuals (4 men, 7 women) from the teacher education program at a major Califomia university
were recruited to participate in the study. Participants did not receive academic credit or monetary
reimbursement for their involvement. They were recruited from a variety of different subject-matter areas
(physics, chemistry, geology, biology, foreign language, English) to provide a range of prior knowledge
for the task phenomena.
Procedure. Participants were presented with a piston/cylinder device (a large 50cc syringe; see Figure 1)
that demonstrated the following three air pressure phenomena:
•
Compression: As the plunger is pushed into the syringe with the nozzle covered by a finger, the
amount of force required to move the plunger increases.
•
Decompression: As the plunger is pulled out of the syringe with the nozzle still covered, the
amount of force required to move the plunger increases.
•
Equilibrium: When the plunger is released after being pushed or pulled, it returns toward its
initial position.
A set of heuristic procedures (see the foregoing) intended to foster understanding through self-generated
analogies was designed. During the task, participants worked alone in the presence of the facilitator
(myself). They were told that the purpose of the study was to examine how they came to produce and
modify explanations about the air pressure phenomena. As a facilitator, I emphasized that I was not
concemed about whether their explanations were correct or not; instead, it was the process by which they
came to understand that was of interest. In spite of these assurances, participants would often look to me
for feedback on their explanations throughout the
covered ~
nozzle ~
syringe/cylinder
Figure 1. Piston/cylinder (syringe) device used to demonstrate air pressure phenomena.
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task. To the best of my ability, I refrained from any substantive or evaluative comments about their
explanations. My involvement in the process was deliberately restricted to giving direction (e.g., generate
an analogy, apply it, explain how it is similar or different from the phenomena) and to providing general
encouragement.
In the first part of the task, participants were asked to explain the three air pressure phenomena. Then, to
identify a significant, meaningful problem specific to their conceptual understanding, participants were
asked to evaluate their explanations and to identify areas that they felt were inadequate. Unlike most
studies of problem solving, participants in this task defined their own problems based on their own
unique understanding of the situation.
In the second part of the task, participants were asked to create their own analogies as a tool for attaining
a better understanding of the phenomena. As it tumed out, the instinct to teach was strong among these
teacher candidates. They would often preface an analogy by mentioning the particular high school class
they were working in at the time. When this happened, they were reminded of the purpose of the analogy:
to help themselves better understand the phenomena, rather than to explain it to a group of students.
After creating an analogy, participants were asked to apply the analogy to the specifics of the air pressure
phenomena, specifying "How is X like Y?" Then, to complement the process of identifying similarities,
participants specified "How is X different from Y?" Participants kept a record of similarities and
differences in a table. After an analogy had been applied and evaluated, participants were asked to modify
the analogy or generate a new analogy. During the course of the hour-long task, this process was repeated
several times, creating a series of continuously evolving analogies and explanations.
Results and Discussion
During the task, participants were audiotaped and videotaped. Transcripts of the tapes were divided into
analogy episodes. The transcripts of the participants' performance were analyzed as a sequence of analogy
episodes. Each episode was characterized by the analogy produced, how the analogy was accessed, how
the analogy was developed, and the influence of the analogy on the participant's explanations of the air
pressure phenomena. The collection of episodes provided a summary of each participant's performance
and an overview of how analogies functioned in the process of conceptual growth. In addition, the
episodes functioned as the unit of analysis for examining the performance for a given individual over time
and the performance between different individuals.
Examples of Change in Explanation through Self-Generated Analogies
To begin the analysis and discussion of the results, two examples of conceptual growth through
self-generated analogies will be presented. The performance of these two individuals was particularly
vivid, although not atypical. Descriptive, narrative excerpts provide the reader with a detailed sense of the
task, the process of analogy use, and the nature of conceptual growth. These excerpts illustrate how
moving through a series of analogies helped participants to clarify, evaluate, and, ultimately, modify their
initial explanations of the air pressure phenomena.
SELF-GENERATED ANALOGIES
373
Barb: People-in-a-room analogy. Barb had an undergraduate degree in biology and was preparing to be a
high school biology teacher. At the beginning of the task, Barb expressed reasonable satisfaction with her
explanation of the compression phenomenon, but felt uncertain about how the decompression
phenomenon occurred. She knew that some sort of vacuum was involved, but was not sure how the
vacuum was related to the force required to pull the plunger out of the syringe. Through her use of
self-generated analogies, Barb focused on the nature of vacuums and, eventually, came to some important
insights.
As a first analogy, Barb began by comparing the syringe phenomena to water boiling at high elevations.
She said this comparison came to mind because "both boiling and the syringe phenomena have something
to do with air pressure." After attempting to specify more precisely how boiling was like the syringe
phenomena, Barb felt that this analogy did not seem to advance her understanding. She admitted that her
weak understanding of the boiling phenomenon made it difficult to generate similarities with the syringe
phenomena.
In her evaluation of the boiling water analogy, Barb mentioned that air is difficult to "see," and, therefore,
was difficult for her to think about. As a result, her next analogy represented the air inside the syringe as
blood, a highly visible, vivid substance. She imagined drawing blood or liquid into the syringe as the
plunger was pulled out. Although this analogy did involve the concept of suction or vacuum, Barb had
difficulty applying this analogy to the air pressure phenomena.
Barb's efforts to compare the airpressure phenomena to otherphenomena involving suction, vacuum, or
air pressure did not seem to lead to clearer understanding. Because her conceptual knowledge was rather
weak in all these domains, she was not able to productively apply explanations from one domain to
another. Compelled and directed by the inadequacies of her analogies to this point, Barb decided to seek a
"nonscience analogy . . . something more down to earth." By moving to a more familiar domain, she
reasoned she could, perhaps, gain a useful perspective on the air pressure phenomena. Immediately after
making this resolution, Barb exclaimed with much excitement and animation in her voice,
Okay, here comes the analogy! It's like crowding people into a room. Let's say there were
100 people in my syringe. Now I'm pushing this plunger in on them, but I close the door.
One of the walls is moving in. So all the 100 people are having to get closer together. But
before we started moving the wall in, they were all mingling like in a party. The walls
start moving in. They're kind of bumping into each other now because there is less space
for them to mingle. So they're starting to also bump into this wall. The is starting to feel a
little force of them bumping into the wall. As the wall keeps coming closer, they keep
bumping into the wall more often. Sort of pushing it back.
At first, Barb was very excited about the people-in-a-room analogy. The comparison provided a
representation that was familiar and easy to visualize: qualities that her prior analogies lacked. However,
while the people-in-a-room analogy seemed to adequately represent the compression phenomenon, Barb
soon realized that this analogy was difficult to apply to the decompression and retum phenomena. Her
initial enthusiasm soon faded as she attempted to explain how people in a room could account for why the
wall would move back in after being pulled out (vacuum).
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Now the wall moves back (as the plunger is pulled out) and they have more room to mingle. So why, why
is there a force on the wall to come back? It's reacting. I don't know. That's where my analogy breaks. See,
if the wall is moving out and they're still moving around. So what, they have more room to move around.
Why are they pulling the wall in?
After a brief pause, Barb made a profound observation:
It's not in here (inside the syringe) where the force is, it must be out here (outside the
syringe) or something.
Instead of seeing the air inside the syringe as accounting for both the compression and decompression
phenomena, Barb began to consider the possibility of the air outside the syringe as having an important
role. This change in perspective represents a major shift in focus, particularly in light of how tactile and
visual cues of the device conspire to establish a perceptual set that focuses attention on the air in the
syringe.
Bert: Rubber-balls-in-a-container analogy. Bert had an undergraduate degree in biology and was
preparing to be a middle school life science teacher. In his initial account of the compression
phenomenon, Bert explains:
In the starting position, there is a certain amount of air in the syringe which means that
there is a certain number of gas molecules. When you cover the opening, you're covering
the only exit for those molecules. Those molecules possess a certain amount of kinetic
energy, a certain amount of motion. In the process of pushing in the piston, you're moving
the molecules closer together than what their kinetic energy would allow. They're
bumping into each other a lot more than they were in the starting position. And thus, the
reason you need more force is because you're getting more resistance from the molecules.
I have no idea if that's right.
The term kinetic energy seemed to represent a central idea in Bert's explanation: "pushing in the piston
moves the molecules closer together than what their kinetic energy would allow." Also, Bert stated that
the molecules bump into each other more as the volume decreases, which creates a resistance. What's
missing in Bert's account is an explicit, causal relationship between volume, collisions, and pressure.
Through a series of self-generated analogies, this central concept became better clarified.
At first, Bert compared the syringe phenomena to compressing a room full of balloons. Bert's evaluation
of this comparison highlighted the analogy's inability to account for the decompression phenomenon. His
next analogy involved stretching a person on a torture rack. This rather vivid comparison captured a
salient aspect of the decompression phenomenon: When the plunger is pulled out of the closed syringe, it
really feels as if something inside is stretching and pulling back in resistance. When the plunger is
released, it snaps back to its original position. Other participants have also compared the decompression
phenomenon to other stretching phenomena such as rubber bands or tugs-of-war.
A central purpose of the evaluation of analogies was to identify differences, as well as similarities,
between the analogy and the phenomenon. For both the balloon and the stretching analogies, Bert
recognized that neither one captured an important feature of all air pressure phenomena: air particles are
in motion. Although these
SELF-GENERATED ANALOGIES
375
compression and decompression, the underlying mechanism by which these phenomena occur was not
represented by the analogies generated to this point.
In his next analogy, Bert made an explicit effon to represent particle motion in his comparison:
The only thing that I'm picturing is just very close to what this is. Only, I'm just picturing
using, um, what am I picturing, I don't know how that works, though . . . I just picture all
kinds of balls moving inside this container. And the container getting smaller and the
pressure needing to get that container smaller is going to increase because . . . Actually as
it gets smaller more and more of those balls are going to be hitting that part that's moving
in, per unit time. The average number of balls that's going to be hitting it is going to be
greater as the volume that those balls are in gets smaller. And that's going to exert a force
going that way on it.
When the rubber-ball analogy was initially created, its purpose was to represent the particles as separate
and moving. However, as Bert applied the analogy, his explanation began to describe the collision of air
particles with the walls of the container. The concept of collision, specifically the relationship between
collisions and pressure, was not mentioned in his initial explanations. (In his initial explanation, Bert
alluded to particles "bumping into each other," but this is quite different from particles colliding with the
walls of the container.) Through the use of this analogy, Bert's explanation has evolved to include a
highly explicit and specific (describing the rate of collisions) description of this important relationship.
Changes in Explanation
In this study, understanding was manifested by the explanations individuals provided to account for air
pressure phenomena. Several definitions are in order at this point. Conceptual growth was defined as a
significant, but not necessarily radical, change in explanation. A change in explanation was defined to
occur when new relationships between aspects of the phenomena were incorporated into an individual's
account for why the phenomena occurred (specific examples are provided later). In describing
understanding or conceptual growth, no attempt was made to move beyond individual's explanations to
explore the nature of knowledge as it might exist "inside the mind of the learner."
Ten of the 11 participants experienced significant changes in their explanations of the air pressure
phenomena through the use of generative analogies. Across the 11 participants, a total of 23 changes in
explanation were noted. Among these changes, several were common to more than 1 individual. These
common changes in explanation were:
• Recognizing the relationship between particle motion, particle collisions, and gas pressure.
• Considering the pressure outside the syringe in explanations of the phenomenon.
• Coming to a better understanding of vacuum
• Making a clearer distinction between pressure and force.
The emergence of common explanations not only describes a shared direction for change, but also
suggests that the analogy generation process addressed common
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preconceptions held by participants. Strike, Hewson, and Gertzog (1982) argue that new understanding
emerges from prior knowledge and the process of change often involves detecting and addressing
preconceptions. In this study, for example, all participants who came to realize the role of outside air
pressure in the phenomenon had previously believed that the air inside the syringe somehow sucked the
plunger in after it had been pulled out. This sucking explanation has been documented by others doing
research on students' understanding of air pressure phenomena (C. W. Anderson, personal
communication, 1990). In another example of change, the relationship between particle motion,
collisions, and gas pressure was established. In this case, many participants had previously believed that
the air pressure was produced by a repulsive force between air molecules.
Stimulating Questions
Changes in understanding were not limited only to changes in the actual explanations of the phenomena.
Insights also came in the form of questions raised about the accuracy or completeness of current
understanding or explanations. Raising questions and developing explanations are often closely related.
Knowledge permitting, questions can frame the problem in a manner that allows new explanations to
emerge (Schon, 1979). Questions raised by participants were categorized into one of two groups:
clarifying existing problems and identifying new problems.
Clarifying existing problems. In some cases, initial questions became more clearly defined and focused as
analogies were generated. For example, following a fairly good initial explanation of the phenomenon,
Cori felt vaguely uncomfortable with her understanding of the concept of pressure.
I wasntt sure of a way to explain pressure, air pressure.... The hardest thing is not understanding
what air pressure is.
Later in the task, Cori was still unsure about exactly what pressure was, but her confusion became better
defined as she began to concentrate on what caused pressure.
[1] have to first decide what air pressure is because I don't really know . . . I don't
know what causes pressure . . . I don't know what force is exerted.
The search to understand the force began to focus Cori's thinking. From here, she soon recalled from prior
learning that collisions between air molecules are the source of the force which causes the pressure. As
was typically the case for other participants, Cori's change in explanation resulted from integrating bits
and pieces of existing knowledge. One might argue that this type of learning is merely recall of forgotten
facts, or that the triggering of associated memory is a random or unpredictable process having little to do
with the analogy. However, Cori's progression through the analogies suggests that she followed a fairly
systematic line of reasoning that may have guided or enhanced the process of accessing prior knowledge.
In her reflections on the task, Cori recalled how she came to recognize the importance of moving,
colliding gas molecules:
I had to find some way to make the translation between the molecules and the
force impmed because pressure is a ~rce So when you faink :rf fmce, you think
|
SELF-GENERATED ANALOGIES
377
of moving objects. So that (that molecules move and collide) was the bridge between gas
molecules and force. Knowing that pressure is a force and that gas molecules are involved in
pressure. I just moved from one to the other.
Focusing of the initial question on the source of the forces seems to have facilitated changes in
understanding.
Discovering new problems. A similar progression of thought, where question refinement is followed by a
change in explanation, is illustrated by Beth. Initially, Beth suspected that a vacuum was somehow
involved in the decompression phenomenon. Beth originally conceived of "vacuum" as a space where the
gas has been removed. However, in the syringe phenomena, gas is not removed from the syringe. This
apparent disparity caused Beth great difficulty and seemed to hamper any progress.
Later in the task, however, Beth began to suspect that vacuum may have a broader definition. Unlike
Cori, who refned her original problem, Beth simply began to have general doubts about her prior
understanding. These general doubts were no more focused than her original problem. However, having
doubts, although ill-defined, can still be viewed as an important component of understanding and of
problem solving. Soon after raising these questions, Beth's explanations for the decompression and return
phenomena changed dramatically.
Unanswered questions: A form of understanding. Not all questions raised during the task led to new
insights. For example, Both Gary and Gail found themselves wondering about the exact difference
between gases and liquids, and how liquids can form at all in light of how difficult it was to compress the
particles together. Although they did not come to a satisfactory explanation of this problem, merely being
able to grasp and articulate the question represents an important growth in understanding (Miyake &
Norman, 1979).
Conclusion
The use of self-generated analogies may facilitate conceptual growth through several time-honored
principles of effective instruction. Constructing one's own analogy serves to (a) make new situations
familiar, (b) represent the problem in the particulars of the individual's prior knowledge, and (c) stimulate
abstract thinking about underlying structure or patterns. (Simons, 1984, and Duit, 1990, provide good
reviews on why analogies are effective.) Furthermore, when students are given the opportunity to work
with their own analogies, three important educational outcomes are served. First, students are provided
with a rare opportunity to problem find, as opposed to simply problem solve. In typical school situations,
problems are well defined and are provided to the students—a situation infrequently found outside of
formal educational settings. Students need to know how to find and represent problems based on the
specifics of their own perception and understanding of the situation. Second, because questions emerge
from the specifics of the leamers' prior knowledge, these questions are likely to be more interesting,
nontrivial, and personally relevant to the learner. Third, individuals can come to identify, confront, and
work through their prior conceptions with minimal guidance from an outsider, such as a teacher. In
instructional situations designed to address misconceptions, the learning environment is often highly
structured to assure that students become aware of the disparity between their understanding and reality.
The teacher then provides an altemative explanation that resolves the conflict and replaces the
misconception (cf. Anderson & Smith, 1986; Osborne & Freyburg, 1985).
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In the generative learning task, finding problems and developing new explanations was guided by the
individual's own understanding and experience, with minimal input from an outside, more knowledgeable
perspective.
Future studies. Presently, I am investigating the nature and potential of selfgenerated analogies with
middle school students. The shift to younger students has highlighted how self-generated analogies are
influenced by the students' subject-matter knowledge and by their understanding of the nature of
analogies. The generation and evaluation of analogies is now occurring within the context of a classroom
community instead of in one-on-one situations. Encouraging a class of middle school students to generate
their own scientific explanations has pointed to critical differences in how participants in the scientific
and classroom communities view leaming and understanding. The use of self-generated analogies
requires a willingness and ability to conjecture, to see the value of one's own ideas, and to view scientific
explanations as tentative and open to evaluation and change. Many social and cultural characteristics of
middle school students and middle school science classes militate against the assumptions underlying the
relationship between self-generated analogies and conceptual growth.
The Role of Self-Generated Accounts in Light of Scientific Authority
Many scientists, educational researchers, and science educators may find a science curriculum that values
and encourages student-constructed explanations to be problematic. Their concerns may by characterized
as follows: Students come to school with an incomplete or incorrect understanding of the natural world.
Allowing students to further develop their own explanations is likely to reinforce their inherent
misconceptions. Is it ethical for teachers to encourage students to develop conceptions about scientific
phenomena that are known to be incorrect? My response to these important concerns is threefold.
First, outside the science classroom (and even while still in science class), individuals will, inevitably,
construct their own accounts of the natural or technological world around them. This ability should be
seen as a gift, rather than an obstacle, to learning and understanding. Science education can be a means of
refining these constructivist tendencies into a more rigorous and systematic way of reasoning about
phenomena.
Second, the process of developing explanations should, when possible, take into account multiple sources
of information. These sources include information from authorities or experts, empirical data generated
from experience and testing, as well as conjectures suggested by analogies. The integration of these
sources of information is central to what is a means to practice responsible science. Scientists not only
conjecture and develop explanations, but they also ground this process upon a foundation of knowledge
generated by others. Therefore, promoting student-generated analogies does not suggest that all
explanations are of equal value, nor does it eliminate the teacher's role as a knowledgeable authority.
Finally, teaching students how to develop, evaluate, and modify their own understanding—particularly if
such activities occur in a social context—is commensurate with teaching them how to comprehend, apply,
and evaluate explanations provided by others. Individuals are constantly encountering scientific accounts
from outside authorities—from doctors, from technicians, from repairmen, from govemment agencies.
One of the goals of science education is to foster a scientifically literate public capable of functioning
effectively as individuals and as members of a democratic society.
SELF-GENERATED ANALOGIES
379
Science instruction, therefore, must provide its students with knowledge and heuristics by which they can
understand, evaluate and decide.
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Manuscript accepted November 5, 1991.