International Journal of Science Education
Vol. 28, No. 5, 14 April 2006, pp. 469–489
RESEARCH REPORT
Modelling Analysis of Students’
Processes of Generating Scientific
Explanatory Hypotheses
Jongwon Park*
Chonnam National University, Korea
[email protected]
00
Dr.
000002005
JongwonPark
International
10.1080/09500690500404540
TSED_A_140437.sgm
0950-0693
Original
Taylor
2005
and
&
Article
Francis
(print)/1464-5289
Francis
JournalLtd
of Science
(online)
Education
It has recently been determined that generating an explanatory hypothesis to explain a discrepant
event is important for students’ conceptual change. The purpose of this study is to investigate how
students generate new explanatory hypotheses. To achieve this goal, questions are used to identify
students’ prior ideas related to electromagnetic induction. After showing conflicting phenomena,
six college students are asked to suggest explanatory hypotheses to explain the phenomena. Using
interviews, the processes of generating explanatory hypotheses are analyzed and three types of
hypotheses suggested by students are subsequently identified: theoretical, experiential, and auxiliary hypotheses. In addition, models of generating each type of explanatory hypothesis are also
suggested. It is concluded that subjects use similarity-based reasoning to relate their background
knowledge or experiences with the conflicting phenomena to be explained. Background knowledge
plays a very important role in generating new theoretical explanatory hypotheses. An example of a
scientific inquiry activity for improving the skill of “generating scientific hypotheses” is also
presented in this paper.
Introduction
Research targeted at developing a deeper understanding of the process of conceptual
change has been a major theme in science education (Behrendt et al., 2001; Limon
& Mason, 2002). According to conceptual change models of science learning, cognitive conflict generated by contradictory evidence is one of the primary factors challenging students’ alternative conceptions of natural phenomena (Darden, 1992;
Limon, 2001; Strike & Posner, 1985). In the philosophy of science, the role of
anomaly in the development of scientific theory has been emphasized. For instance,
a naive falsificationist insists that the scientific theory should be discarded without
*Department of Physics Education, Chonnam National University, Gwangju 500–757, Korea.
Email: [email protected]
ISSN 0950-0693 (print)/ISSN 1464-5289 (online)/06/050469–21
© 2006 Taylor & Francis
DOI: 10.1080/09500690500404540
470 J. Park
any prevarication, when any observations or experimental results contradict a theory
(Lakatos, 1994, p. 13).
However, from the history of science, many instances demonstrating that scientific
theories still survive, even with conflicting data, can be found. For instance, Kuhn
(1970, p. 81) said:
… even a discrepancy unaccountably larger than that experienced in other applications
of the theory need not draw any very profound response. … No one seriously
questioned Newtonian theory because of the long recognized discrepancies between
predictions from that theory both the speed of sound and the motion of Mercury.
Chalmers (1986, p. 61) stressed “Nothing in the logic of the situation requires that it
should always be the theory that is rejected on the occasion of the clash with observation,” and illustrated some examples in the “The limitation of falsification”
section of his book. Physicist Dirac (1981, pp. 91–92) also asserted:
If a discrepancy should appear in some application of the theory, it must be caused by
some secondary features relating to this application which has not been adequately
taken into account, and not by a failure of the general principles of the theory.
In addition, psychological research demonstrating the different ways students can
respond to anomalous observations, rather than simply rejecting their prior ideas,
can also be found. For instance, Gauld (1986) observed that even though a student
correctly reads data conflicting with his/her prior idea, after 3 months he/she reconstructed his/her memory of observation to remain consistent with the prior idea; and
Shepardson et al. (1994) also observed that demonstration designed to support new
conceptual understandings reinforced students’ prior understanding rather than
generating a cognitive conflict. According to Chinn and Brewer’s (1998) taxonomy
comprising seven types of responses to anomalous data, students may ignore, reject,
or exclude conflicting data. Students may try to reinterpret anomalous data or
change data only as a peripheral theory, in order to preserve the core of their prior
theory, when they are forced to accept or believe conflicting data. In addition,
students may hold anomalous data in abeyance, waiting for somebody else to solve
the discrepancy.
This means that conflicting experimental data alone do not guarantee falsification
of a theory. Therefore, Lakatos and Kuhn note that, in addition to the conflicting
observations, a new alternative explanatory hypothesis, capable of explaining the
anomaly, should be introduced to falsify the core scientific theory.
… no experiment, experimental report, observation statement … alone can lead to falsification. There is no falsification before the emergence of a better theory. (Lakatos,
1994, p. 35)
once it has achieved the status of paradigm, a scientific theory is declared invalid only if
an alternate candidate is available to take its place. (Kuhn, 1970, p. 77)
Park and Kim (1998) found that, when students were confronted with contradictory experimental results relating to the brightness of a bulb in a simple electric
circuit, almost all the students who changed their preconceptions generated a new
Scientific Explanatory Hypotheses 471
explanatory hypothesis to explain the contradiction. In the study analyzing students’
processes of falsification of their prior ideas regarding electrostatics, Park, Kim,
Kim, and Lee (2001) also observed that contradictory observations alone, without
any new alternative explanatory hypothesis, could not falsify the core of their
conception. Driver (1988, p. 41) notes that allowing the students opportunities to
refute their prior ideas is not a complete answer, because students’ prior misconceptions will not be rejected until there is something adequate and reliable to replace it.
Therefore, Driver stresses that opportunities should also be provided for students to
explicitly generate alternative interpretations of a conflicting event; that is, to invent
their new hypotheses (1988, p. 48).
This study began with the purpose of exploring and creating a clear understanding
of the method in which students generate new explanatory hypotheses for explaining
conflicting experimental results.
Some researchers in the area of science education and philosophy of science are not
interested in the process of generating a new hypothesis. For instance, Popper asserts
that the initial stage of inventing a new hypothesis does not call for logical analysis;
therefore, the question of how a new hypothesis occurred to a scientist’s mind may be
of interest to empirical psychology and is irrelevant to the logical analysis of scientific
knowledge (Popper, 1968, p. 31). Popper further asserts that a scientific hypothesis
is just a guess, a free creation of a scientist’s mind, and the result of an almost poetic
intuition (p. 192). Physicist Feynman (1965), summarizing the process of scientific
investigation, also states that a new idea in the initial stage of investigation appears by
“guessing,” but he does not give any detailed information regarding the process of
“guessing.”
Contrary to Popper or Feynman’s view, Peirce (1955) argues that even though the
process of creating a new hypothesis involves a psychological factor, it can also be
viewed as a rational process. Hanson (1961) also criticizes the view regarding the
generation of a hypothesis as being of psychological interest only, and asserts that
conceiving a hypothesis has logic (p. 71). Hanson summarizes the form of inference
of generating a new hypothesis as follows (p. 86):
Some surprising phenomenon P is observed.
P would be explicable as a matter of course if H were true.
Hence, there is reason to think that H is true.
In relating to this kind of inference, the main research questions in this study
relate to the processes the students actually execute when generating new hypotheses, what features are there in new hypotheses suggested by students, and which
types of thinking are involved in the processes of generating hypotheses.
In regard to the last question, at a Harvard lecture in 1903, Peirce noted that
“Abduction is the process of forming an explanatory hypothesis. It is the only logical
operation which introduces any new idea” (1998b, p. 216) and “All the ideas of science
come to it by the way of abduction. Abduction consists in studying facts and devising
a theory to explain them” (1998a, p. 205). Hanson also insists that formulating new
472 J. Park
ideas are not sourced from induction or deduction, but from abduction that “involves
sensing ways in which the current situation is somehow similar (analogous) to other
known situations and using this similarity as a source of hypotheses in the present
situation” (Lawson, 1995, p. 7).
It is important to discover whether these abductive inferences can also assist the
students in inventing new explanatory hypotheses. Unfortunately, very little research
exists investigating the process of generating a hypothesis in the context of students’
study of science. The focus of this study is on exploring the types of thinking, including abductive inferences, that actually play on the students’ process of generating
new explanatory hypotheses in order to explain an unexpected phenomenon.
Definition of Explanatory Hypothesis
The most widely used definition of hypothesis in science education is to view scientific hypothesis as the tentative causal explanation regarding an observed effect
(Wenham, 1993). For instance, Quinn and George (1975) defined a hypothesis as a
testable explanation of an empirical relationship among variables in a given problem
situation, and Fisher, Gettys, Manning, Mehle, and Baca (1983) argued that
hypothesis generation is the process of creating possible, alternative explanations for
a given set of information. In this study, this view is adopted as a definition for
explanatory hypothesis.
Purpose of this Study
This study was designed to:
1. describe the processes of generating new explanatory hypotheses;
2. identify the major features of hypotheses that students suggest; and
3. find out the types of thinking for generating new hypotheses.
Procedures
Instruments
The main question used in this study is described in Figure 1. The basic concept
involved in this question involves electromagnetic induction. When a magnet falls
inside an aluminum pipe, the magnetic field around the aluminum pipe changes, an
electric current is induced in the aluminum pipe (by Faraday’s Law), and this
induced current generates a new magnetic field. Through the interaction between
the magnetic field of a magnet and the induced magnetic field produced by the
induced current, a magnet falls slowly with a constant velocity.
When students are requested to predict through which pipe, aluminum or plastic,
a magnet will fall first, many students predict the two magnets will fall at the same
rate because aluminum and plastic are not attracted to a magnet. Interestingly, many
Figure 1. Main question.
Scientific Explanatory Hypotheses 473
Magnet A
Magnet B
Aluminum Pipe
Plastic Pipe
Which magnet falls first
if a magnet is dropped inside a pipe?
Explain the reason
Figure 1.
Main question.
students do not recognize the phenomena of electromagnetic induction when a
magnet falls inside an aluminum pipe. For this study, only students who predicted
the two magnets inside the aluminum pipe and plastic pipe would fall at an equal
velocity were selected as subjects. After demonstrating a magnet inside an aluminum
pipe falling slower, students were prompted to suggest a hypothesis to explain the
phenomenon.
According to Lakatos (1994, p. 33), scientific theory should be appraised together
with its auxiliary hypotheses, initial conditions, and other related theories. Therefore, concern should be for a series of theories, rather than for an isolated theory.
This means that it should be required to obtain information regarding the subjects’
various ideas relating to the core idea of the main question in Figure 1. To achieve
this, additional questions related to basic knowledge about electricity and magnetism are used to identify students’ prior knowledge state (referred to as “supplementary questions”). For instance, which materials are attracted to a magnet? Which
materials can conduct electric current? Which part of the coil is the N pole when
electric current flows in a coil? When do we use a galvanometer?
In the supplementary questions, no question regarding electromagnetic induction
is included because such a question might provide indirect hints in explaining the
conflicting phenomena.
Subjects
Six college students, with an average age of approximately 19 years, participated in
this study. They were randomly sampled from the total number of students in the
author’s department. Prior to interview, the purpose of the interview was explained
and only students agreeing with the purpose participated in the interview. All participants majored in physics education and were taking an introductory physics course,
but had not studied the electricity and magnetism unit in the course when this
research began.
474 J. Park
Table 1.
Q1-1
Q1-2
Q1-3
Q1-4
Main questions used in the first interview
“Can you describe what you observe?” or “What do you observe?”
“Do you have any questions related to your observation?”
“Can you explain your observation?” or “Can you explain what you observed
more precisely?”
“[if subject explains observation] How do you know that?” or “What is the
reason for your explanation?”
Interview
The interviews were conducted in two stages. The first interview was conducted
after presenting an experiment (the “Target Experiment” [TE]) in which a magnet
inside the aluminum pipe fell slower. The main questions used in the first interview
are presented in Table 1.
When the TE was presented, students were expected to suggest explanatory
hypotheses explaining the TE. However, as we know, generating a new explanatory
hypothesis spontaneously is very difficult work. Therefore, after the first stage of the
interview, the researcher demonstrated three additional experiments (the “Clue
Experiments” [CE]) from which subjects were able to obtain clues for explaining the
TE. Figure 2 illustrates the three CEs.
From the first CE, students may realize or recall the fact that moving a magnet
inside the coil generates an electric current. From the second, students understood
that a compass moves due to the magnetic field generated around the electric
current. From the third, students directly feel force acting on his/her hand when he/
she moves a magnet into a coil. All three CEs can be used to explain the TE.
However, the researcher did not give any explanation about possible relationships
between the CEs and the TE. When the CEs were demonstrated, the researcher
explained to the students that each of the three experiments may or may not be used
for explaining the TE.
Figure 2. Three Clue Experiments.
Figure 2.
Three Clue Experiments.
Scientific Explanatory Hypotheses 475
Table 2.
Q2-1
Q2-2
Q2-3
Q2-4
The questions used in the second interview
“Can you describe what you observe?” or “What do you observe?”
“Do you have any questions about this [clue] experiment?”
“Do you think this experiment [among the three CEs] is related to the phenomenon
that a magnet falls slowly inside the aluminum pipe?”
“[if subjects say yes] How is this experiment related to that phenomenon [TE]?”
After demonstrating the CEs, the second interview was conducted. The questions
used in the second interview are presented in Table 2.
After demonstrating the three CEs and interviewing subjects with the aforementioned questions, subjects were again asked to explain why the magnet inside aluminum
pipe fell slower.
The procedure for obtaining data is summarized in Figure 3. Two interviews were
conducted successively; that is, there was no time delay between the first interview
and the second.
After completing interviews, students’ interview protocols were categorized
according to the main questions used in the interviews (Tables 1 and 2), and then
the processes of generating new explanatory hypotheses could be drawn step by step.
The responses in each step when generating hypotheses were classified according to
their characteristics. Then, based on the analyzed characteristics, the types of
hypotheses, important factors affecting the generation of hypotheses, and the type of
thinking for generating hypotheses were identified.
Figure 3. Summary of the procedure.
Results
Students’ Prior Ideas
As mentioned earlier, before observing the TE all six college students predicted that
a magnet inside an aluminum pipe would fall as fast as a magnet inside a plastic
pipe. In addition to the central question, supplementary questions were asked
regarding basic concepts related to electricity and magnetism. An analysis of the
students’ answers revealed that all students had a sound understanding of the
supplementary questions. That is, all students were able to identify those materials
that could be attracted to a magnet and which materials could conduct electric
current. Furthermore, they all knew which part of the coil was the N pole when
Step 1: Answering the main question (Fig. 1) and supplementary questions
Step 2: Observing the Target Experiment (TE) and explaining the TE in the first interview
Step 3: Observing the Clue Experiments (CEs) (Fig. 2) and explaining the TE again in the
second interview
Figure 3.
Summary of the procedure.
476 J. Park
electric current flowed through the coil, and understood that a galvanometer was
used to measure electric current.
Process of Generating an Explanatory Hypothesis in the First Interview
The process of generating a hypothesis was identified and summarized in Figure 4,
based on the analysis of students’ responses in the first interview. Initially, students
observed the TE in which a magnet fell slower inside an aluminum pipe; then, in the
second stage of the process, students asked a causal question, such as “Why does a
magnet fall slowly?” Of course, the students asked this question spontaneously, not
the researcher. The students then searched for a hypothesis that could explain the
TE, finally suggesting a hypothesis they felt was appropriate.
This process is summarized in the upper boxes of Figure 4; in the lower boxes,
major characteristics of the students’ responses are described. Capital letters of the
alphabet in each stage indicate particular students.
Initially, when generating a new hypothesis (Figure 4), and observing the TE,
some students (Students A, B, E, and F) simply glanced at the TE. Others (Students
C and D) explored the TE further. For instance, some students looked inside the
pipe and carefully observed the motion of the falling magnet, listened to the sound
generated by the collision between the falling magnet and the interior wall of the
pipe, or brought a magnet into contact with the aluminum pipe to test whether a
magnet attracted the aluminum.
Prior to observing the TE, all students predicted both magnets would fall at equal
speeds, but they observed that one magnet fell slower. Therefore, at the second stage
in the process of generating an appropriate hypothesis, they all asked why a magnet
falls slower when inside an aluminum pipe.
At the third stage, Students A and E searched for hypotheses in their Background
Knowledge (BK) relating to electromagnetic theory. The following is an example of
a student’s response:
Figure 4. The process of generating a hypothesis in the first interview.
ABCDEF
Observing
the target
experiment
ABCDEF
ABCDEF
Asking
causal
question
Searching
for
hypothesis
EF
No
hypothesis
Suggesting
hypothesis
ABCD
Just
looking
ABEF
Exploring
the Target
Experiment
CD
Figure 4.
Background
knowledge
Experimental
context
Theoretical
hypothesis
Auxiliary
hypothesis
AE
BCD
A
BCD
The process of generating a hypothesis in the first interview.
Scientific Explanatory Hypotheses 477
… I know that if a magnet moves inside a coil, then electricity is generated … when a
magnet accelerates. … if speed (of a magnet) is constant, then electricity is not generated. This is similar to the law of inertia. … I know also that there is an electromagnetic
force … then, can electric force and magnetic force be viewed as the same thing?
…(Student A)
Student A recalled that an accelerated magnet inside a coil could generate electricity
and then asked himself whether electricity and magnetism were fundamentally the
same. Here, information recalled by Student A was not provided by the interviewer—such information was retrieved spontaneously from the student’s BK. Of
course, Student A’s BK was not scientifically correct. That is, the condition that a
magnet should accelerate to induce electric current in a coil is not necessary.
Constant motion of a magnet may also induce electric current.
In the third stage, Students B, C, and D searched for a hypothesis in the experimental context. The following are examples of the students’ responses:
… if the thickness [of two pipes] are equal [with each other], … and if a magnet did not
touch the pipe…(Student B)
When a magnet falls inside a pipe, the magnet touches the wall of the pipe. (Student C)
[comparing the diameter of two pipes] The diameter of the plastic pipe looks larger than
… the same? … I want to measure it precisely … (Student D)
Students B, C, and D were concerned only with experimental features such as the
diameter of the pipe or a collision between a falling magnet and the pipe.
Types of Explanatory Hypotheses Suggested by Students: Theoretical and auxiliary hypothesis
In the final stage of the first interview, Student F did not generate a hypothesis
explaining the TE. Student E attempted suggesting a hypothesis and expressed the
idea that “There may be force …” However, when he was asked how the force was
generated and what the force was, he was unable to give any explanatory responses.
Student E was therefore not regarded as having suggested a new explanatory
hypothesis.
In the final stage of the first interview, four students (Students A, B, C, and D)
suggested a new explanatory hypotheses, and their hypotheses could be classified
into two types: theoretical hypothesis (Student A), and auxiliary hypothesis
(Students B, C, and D). Student A’s theoretical hypothesis included a theoretical
causal relationship between the “effect” that a magnet inside the aluminum pipe falls
slowly and the “cause” of electromagnetic theory. The following is an example of the
theoretical hypothesis suggested by Student A:
If a magnet accelerates inside the [aluminum] pipe, then electricity is generated … then
+ and − electricity is generated at the top and bottom of the pipe respectively … then
the upward directional force acts [on a magnet] …
In this suggestion, Student A attempted explaining the TE using electromagnetic
induction (“If a magnet accelerates inside the [aluminum] pipe, then electricity is
478 J. Park
generated”) and the force generated by the interaction between electricity and
magnetism (“+ and − electricity are made at the top and bottom of the [aluminum]
pipe respectively … then the upward directional force acts [on a magnet]”). Of
course, his explanation was not scientifically correct. That is, Student A thought +
and − electricity were both generated at the top and bottom of the pipe by accelerating a magnet. However, electricity is generated by the constant movement of a
magnet, and also, he misunderstood that + electricity (or – electricity) could attract
the N pole (or S pole) of a magnet. This type of misconception is constructed by not
discriminating between electricity and magnetism. However, the point is that
Student A discarded his prior idea that a magnet inside an aluminum pipe falls at the
same rate as a magnet inside a plastic pipe, and suggested a new hypothesis to
explain the conflicting observation.
Conversely, Students B, C, and D preserved their prior ideas and attempted to
attribute the reason of the conflicting phenomenon of the TE to experimental
contexts. The explanations provided by Students B, C, and D are as follows:
It might be due to the friction … a magnet is hitting the [inner] wall [of the pipe] while
it is falling down. (Student B)
If the shape of a magnet is spherical, then … the magnets will fall at the same rate. A
magnet falls slower because the shape [of a magnet] is cylindrical … then, the surface
[of a magnet] in contact with the pipe varies as the magnet falls, … therefore the magnet
falls slower. (Student C)
It … might be due to the air resistance, because this gap [indicating the gap between a
magnet and the inner wall of the pipe] is too narrow … (Student D)
In these cases, even though the TE seemed to conflict with their prior ideas,
Students B, C, and D thought that the result of the TE was due to the experimental
conditions. That is, they thought that a magnet would fall inside an aluminum pipe
equally with the magnet inside a plastic pipe if friction and air resistance could both
be removed, or if the shape of the magnet was spherical. These responses are very
similar to the Lakatosian view of falsification of scientific theory. According to Lakatos (1994), although experimental evidence may contradict a theory, the core of the
theory can be maintained by adjusting the protective belt around the core, either by
suggesting auxiliary hypotheses, modifying initial conditions, or giving suitable reinterpretation of its terms (Lakatos, 1994, p. 32). Therefore, I call these hypotheses
“auxiliary hypotheses.” This type of response can also be found in other studies.
Park et al. (2001) observed that many junior high school students, when they
observed conflicting evidence, only modified their protective belt by suggesting
auxiliary hypotheses rather than rejecting or changing the core of their prior ideas.
The Role of Background Knowledge in Generating Theoretical Hypotheses
When comparing two types of hypotheses (theoretical or auxiliary), an interesting
aspect was found. Except for Students E and F, who failed to generate a hypothesis,
Student A, who searched for a hypothesis in his BK relating to electricity and
Scientific Explanatory Hypotheses 479
magnetism, suggested a theoretical hypothesis, while students B, C, and D, who
searched for a hypothesis in the experimental context, all suggested auxiliary
hypotheses. This means that the detailed and elaborated observation or exploration
of the TE alone does not lead to the suggestion of a new explanatory hypothesis that
can explain the TE with an internal theoretical causal relationship. This finding
reminds me of Hempel’s explanation regarding generating scientific hypotheses:
“Scientific hypotheses are not derived from observed facts, but invented in order to
account for them” (1965, p. 15).
This also means that background knowledge is important in generating new
explanatory hypotheses involving theoretical causal relationships. The importance of
background knowledge in generating hypotheses can be seen in literature. For
instance, in the area of scientific creativity, it has been accepted that knowledge of the
field is important for creating a new invention (Cropley, 1999). It has also been
pointed out that scientific intuition, leading to new discovery, relates not to commonsense experience, but to highly specified knowledge (Wolpert, 1992, p. 64).
Similarity-based Reasoning for Generating a Theoretical Explanatory Hypothesis
In the process of generating hypotheses, another valuable question relates to the type
of thinking involved when students invent new theoretical explanatory hypotheses.
To obtain information regarding this question, after Student A suggested theoretical
hypotheses, he was asked “How do you know that?” or “What is the reason for your
explanation?” It was found that Student A suggested a new theoretical hypothesis
based on the similarity between the BK related to electromagnetic theory and the
TE. The following are examples of Student A’s responses:
When a magnet moves back and forth [inside the coil], it accelerates, then electric
current is generated. … Likewise, when a magnet falls inside the pipe, it accelerates due
to the gravity, therefore electric force may be generated …
…
The coil is a conductor and also the aluminum pipe a conductor … the wire [of coil]
encloses the magnet, and also this [aluminum pipe] encloses the magnet.
During the first stage of the interview, the researcher did not present any experiments using a coil and magnet, and did not provide any information related to electromagnetic theory. However, in Student A’s first response, he linked his BK of
electromagnetic induction that an electric current is generated when a magnet
moves (with acceleration) inside a coil to the fact that a magnet falls (with acceleration) inside an aluminum pipe. As mentioned earlier, to induce an electric current in
a coil or an aluminum pipe, the condition that a magnet accelerates is not required.
The point here is simply that Student A inferred that two aspects (BK regarding
electromagnetic induction and the phenomenon of a falling magnet an inside aluminum pipe) were similar in that two magnets move with acceleration. Furthermore, in
the second response, he recognized that the coil in his BK and the aluminum pipe in
480 J. Park
Background Knowledge (BK) has properties α, β, and γ.
Target Experiment (TE) also has similar properties α’, β’, and γ’.
Then, the BK and TE share similar properties with each other.
The BK has another property δ.
Therefore, it is worth inferring that TE will also have property δ’,
even though δ’ has not yet been confirmed.
Figure 5.
Model of similarity-based reasoning.
the TE shared similar superficial features—that they (coil and aluminum pipe) were
conductors and equally enclosed the magnet.
This type of thinking can be regarded as “similarity-based reasoning.” This
reasoning is summarized in Figure 5.
According to the model of similarity-based reasoning (Figure 5), Student A’s BK
corresponds to basic knowledge related to electromagnetic induction theory, property α corresponds to the condition that a magnet should move (with acceleration),
β to the fact that the coil is the conductor, and γ to the situation in which the coil
encloses a magnet. Similarly, α′, which is the property of the TE, corresponds to the
situation in which a magnet moves (with acceleration due to gravity) when it falls, β′
to the fact that the aluminum pipe is a conductor, and γ′ to the situation in which the
pipe also encloses a magnet.
The property δ of the BK corresponds to the fact that current is induced in the
coil. Therefore, property δ′, which cannot be observed directly in the TE, corresponds to the new property where the current will be generated from the aluminum
pipe. As a result, Student A could suggest a new hypothesis that a magnet falls
slower inside an aluminum pipe because of the induced current in the aluminum
pipe due to the (accelerated) motion of the magnet.
Using Clement’s bridging analogies, similarity-based reasoning (Clement, 1987)
can be encouraged. To promote a change in the misconception that there is no
upward force—normal force exerted by table—acting on a book sitting on the table,
Clement used a familiar situation with students, that a spring exerts an upward force
on one’s hand when one holds and compresses it.
Here, the point is that two situations—the book on the table and the compressed
spring—share similar properties. This means that, if students can recognize those
similar properties, they are willing to draw the conclusion that the table exerts an
upward force on the book. Clement’s bridging analogy strategy may therefore be a good
teaching strategy to promote conceptual change using similarity-based reasoning.
Figure 5. Model of similarity-based reasoning.
Scientific Explanatory Hypotheses 481
Observe discrepant Target Experiment (TE) to be explained
Ask causal question why TE happens.
Search for hypothesis that may explain the TE in the observer’s Background Knowledge (BK).
Use similarity-based reasoning between TE and BK.
Discard prior theory relating to TE, and suggest new theoretical hypothesis that can explain TE.
Figure 6.
Model of generating a theoretical explanatory hypothesis using similarity-based
reasoning.
Now, based on the four stages of generating a theoretical explanatory hypothesis
in Figure 4 and the similarity-based reasoning model in Figure 5, the model of
generating a new theoretical explanatory hypothesis using similarity-based reasoning
is described in Figure 6.
Contrary to the process of generating a theoretical hypothesis, in the process of
generating an auxiliary hypothesis, students explore actual experimental situations,
rather than searching for their hypotheses in their BK relating to electromagnetism.
As a result, the reason of the discrepant experimental result was attributed to the
experimental conditions, consequently preserving their prior ideas.
Of course, during exploration of the experimental situation, Students B, C, and D
also used knowledge such as air resistance or frictional force acting on a moving object
resisting the motion of the magnet. However, this knowledge is connected directly to
the observation of the TE, and therefore similarity-based reasoning was not used in
this process. Conversely, Student A’s BK was remote to the observation itself, and
therefore he could determine whether information derived from the BK shared similar properties with the TE. More specifically, similarity-based reasoning played an
important role in Student A’s thinking process. This is the difference in thinking
between the process of generating a theoretical explanatory hypothesis and an auxiliary hypothesis. Figure 7 describes the process of generating an auxiliary hypothesis.
Figure 6. Model of generating a theoretical explanatory hypothesis using similarity-based reasoning.
Figure 7. Model of generating an auxiliary explanatory hypothesis.
Process of Generating an Explanatory Hypothesis in the Second Interview using Clue
Experiments
As mentioned earlier, generating a new explanatory hypothesis spontaneously is not
easy. Therefore, three CEs were prepared to provide clues to students as to which
could be used to explain the TE.
In the second interview, all students observed these three CEs. However, because
the researcher noted that the prepared CEs may or may not be related to the TE,
students had to determine whether or not each CE could be used to explain the TE.
How students related the CEs to the TE will be discussed in subsequent sections.
482 J. Park
Observe Target Experiment (TE) to be explained.
Ask causal question as to why TE occurs.
Search for hypothesis that may explain the TE in the experimental situation of TE.
Preserve prior theory relating to TE, and suggest auxiliary hypothesis
attributing the reason for the TE to experimental conditions.
Figure 7.
Model of generating an auxiliary explanatory hypothesis.
Based on the analysis of students’ responses in the second interview, the processes
of generating new explanatory hypotheses using CEs are illustrated in Figure 8.
In the first stage of the process of generating hypotheses in the second interview,
when three CEs are demonstrated, Students A, B, C, E, and F just looked the
experiments. However, Student D explored the experiment closely. By pushing and
pulling a magnet into a coil of the third CE, she compared the strength of the force
acting on a magnet by varying the speed of the moving magnet.
Figure 8. The process of generating a hypothesis in the second interview.
… I can feel resistance [acting on the magnet] when I push and pull a magnet. … feel
more resistance when I move it fast …(Student D)
ABCDEF
B
Observing
the clue
experiments
(CEs)
No Relating
the CEs
with the TE
B
Maintaining
original
hypothesis
A
ACDEF
Relating
the CEs
with the TE
Suggesting
new
hypothesis
CDEF
Background
Knowledge
Just
looking
Exploring
the CEs
Experimental
similarity
Reference
book
Theoretical
hypothesis
ABCEF
D
ACEF
D
D
Figure 8.
Experiential
hypothesis
CEF
The process of generating a hypothesis in the second interview.
Scientific Explanatory Hypotheses 483
In the second stage of the second interview, all students except Student B believed
that the CEs were related to the TE. Among them, Students A, C, E, and F related
the CEs to the TE, based on the experimental similarities between them. The
following demonstrate examples of students’ responses mentioning the similarities
between the CEs and the TE:
Interviewer:
Student C:
Student E:
Interviewer:
Student F:
Are these [indicating three CEs] related to the former experiment [TE]?
These [coil in CE and aluminum pipe in TE] are metal … share similar
properties … electricity can flow [in a coil and aluminum pipe] …
This [indicating coil in the third CE demonstrating the force acting a
magnet moving inside a coil] is related with that [indicating aluminum
pipe in TE]. These [coil and aluminum pipe] are equally metallic…
Do you think this coil [of CE] is related to the aluminum pipe [of TE]?
This coil is made of enameled copper wire…
Yes… because two [coil and aluminum pipe] are all conductors.
However, Student D related background knowledge to the electromagnetic theory
and searched for relevant information in a textbook:
[after observing three CEs] the N pole of a magnet… enters into a coil, then electric
current is generated … this is learned in high school… in this case, force can be
explained by the right hand [rule] … [and she requested a high school physics textbook,
and read the figure and explanation concerned with the electromagnetic induction using
a magnet and coil]
In the third stage, Student B, suggesting an auxiliary hypothesis in the first interview, failed to suggest a new explanatory hypothesis even though he observed the
three CEs. As a result, he maintained his original auxiliary hypothesis.
Student A also maintained his original theoretical hypothesis suggested in the first
interview. In this case, he viewed CEs as supporting evidence to his theoretical
hypothesis suggested in the first interview. The following is Student A’s response:
I said that the force acts [on a magnet] when a magnet moves inside an aluminum pipe.
In the same manner, here, when I push a magnet into a coil, the force acts [on a
magnet].
Student D, searched for a hypothesis in her BK relating to electromagnetic theory
and, using a high school physics textbook, suggested a new theoretical explanatory
hypothesis as follows:
If a magnet is pushed into a coil, then an electric current is induced, and it [the coil]
becomes a magnet due to that [induced] electric current. Here, if the N pole of a
magnet approaches [the coil], then the N pole is generated in the coil, therefore, this [N
pole of a coil] repels the magnet. This force resists the gravity.
Another Type of Explanatory Hypothesis: Experiential hypothesis
In the third stage, Students C, E, and F, failed to suggest a new theoretical hypothesis in the first interview, but generated new hypotheses using the CEs in the second
interview. However, their hypotheses were different from the theoretical or auxiliary
484 J. Park
hypothesis. That is, they rejected their prior prediction and suggested a new
explanation regarding the TE. However, there was no theoretical causal relationship
in their explanation. In this case, their prior prediction was discarded and a new
explanation based on similarity-based reasoning was suggested, not between the TE
and the BK, but between the TE and the CEs. The following is Student C’s
response:
There should be [an upward] force [acting on a magnet in the TE] … because I felt
force when the magnet was pushed into a coil [in the third CE].
Here, Student C inferred that force acted on a magnet falling inside an aluminum
pipe in TE, based on his experience that he felt the force acting on the magnet when
he pushed the magnet into the coil of the third CE. However, Student C did not
explain this force was generated. That is, he did not explain the reason or cause of
the force theoretically. His hypothesis was based only on the experience from the
CE. Therefore, I called this hypothesis suggested by Student C an “experiential
hypothesis.”
The hypothesis suggested by students E and F may also be viewed as an experiential hypothesis. The following is Student E’s response:
The reason that a magnet falls slowly inside an aluminum pipe [in TE] is because there
is a force between them [aluminum pipe and a magnet]. … here [indicating the second
CE demonstrating magnetic force acting on a compass needle by electric current],
something [indicating the moving needle of a compass] is also changed… because of a
force.
Student F also inferred that force should act on a magnet falling inside an aluminum
pipe, using the experience that an electric current interacts with a magnet in the
second CE. However, he did not explain why electric current is generated in the
aluminum pipe, and did not explain theoretically how the electric current can interact with the magnet. His hypothesis was based only on his experience with the CEs.
Student F:
Interviewer:
Student F:
Interviewer:
Student F:
Interviewer:
Student F:
There may be electric current [in the aluminum pipe of the TE].
How do you know that?
By observing this [the first CE demonstrating electric current induced in
the coil by moving magnet inside a coil].
Okay, electric current flows, and then?
If the electric current flows [in the aluminum pipe] … then, electric
current can respond to a magnet …
How do you know that?
If electric current flows, then the needle of compass [in the second CE]
moves, and the compass is also a magnet.
From the first CE, Student F first obtained the clue that electric current can be
generated when a magnet moves, and then, from the second CE, he obtained the
second clue that electric current can interact with the magnet. Using these two
clues, Student F inferred that if a magnet moves inside an aluminum pipe, electric
current is generated, and this electric current could make a magnet fall slowly. Yet,
in this case, there was also no theoretical relationship between the cause and the
Scientific Explanatory Hypotheses 485
Observe discrepant Target Experiment (TE) to be explained.
Ask causal question.
Observe Clue Experiments (CE), which can be used to explain the TE.
Relate TE to CE based on the similarities between the two phenomena.
Discard prior theory related to TE, and suggest new experiential hypothesis
based on the similarities between CE and TE.
Figure 9.
Model of generating an experiential hypothesis.
effect. Student F suggested his hypothesis based only on his experience with the
CE.
In the case of the experiential hypothesis, the thinking pattern of hypothesis
generation can be summarized in Figure 9.
Figure 9. Model of generating an experiential hypothesis.
Suggestion for Teaching “Generating an Explanatory Hypothesis”
According to the suggested models of theoretical or experiential hypothesis (Figures
6 and 9), the process of generating a new explanatory hypothesis can be summarized
as follows: making observation → asking causal question → searching for hypothesis
in the background knowledge or relevant experiments (phenomena) using similaritybased reasoning → suggesting a new explanatory hypothesis.
This process of generating an explanatory hypothesis can be used to develop
teaching plans for scientific inquiry activities including the inquiry skill of “generating scientific hypothesis.” An example of this activity is described in Figure 10.
The scientific inquiry activity in Figure 10 is comprised of four stages according to
the model of generating scientific hypotheses. Step 1 corresponds to “making observation,” and the observation can be described as follows: The nail does not attract
the paper clip initially, but after rubbing the nail with a strong magnet, the paper clip
is attracted.
Step 2 corresponds to “asking causal questions.” Here, students can ask following
questions: Why does the nail attract the paper clip after rubbing the nail with the
magnet? How does the nail become a magnet?
In Activity 3, students attempt answering the question asked in Step 2. That is,
they try to generate a new scientific hypothesis, used to explain the observation in
Step 1. The answer may be that rubbing it with a strong magnet magnetizes the nail.
However, the process of magnetization cannot be directly observed, so it is not easy
for students to generate a scientific hypothesis that can explain these phenomena.
Figure 10. Scientific inquiry activity for generating a scientific hypothesis.
486 J. Park
Figure 10.
Scientific inquiry activity for generating a scientific hypothesis.
Steps 4 and 5 are therefore provided to help students “searching for a hypothesis.”
In Step 4, even though materials inside a glass tube are magnets, they cannot attract
the paper clip because small pieces of broken magnets are randomly arranged. As a
result, magnetic fields negate each other. However, if students rub the glass tube
with another strong magnet, then small pieces of the broken magnets inside the tube
can be arranged uniformly and can attract the paper clip.
Step 5 is provided to encourage students’ similarity-based reasoning. If students
recognize there are similarities between the result of Step 1 and the phenomena in
Step 4—for instance, the paper clip is not attracted to the nail or small pieces of
broken magnets inside a glass tube in the first trial, but is attracted after rubbing it
with strong magnet—it is plausible to infer that the nail may be composed of small
pieces of magnets.
Finally, Step 6 corresponds to “suggesting a new explanatory hypothesis.” For
instance:
The nail also may have small pieces of magnet inside. Under ordinary circumstances,
these small magnets are arranged irregularly, therefore a magnetic field does not appear.
However, if the nail is rubbed with a strong magnet, the small magnets inside the nail
can be arranged uniformly. As a result, the nail can attract the paper clip.
Scientific Explanatory Hypotheses 487
If students generate their hypotheses based only on the similarities between the
observations in Steps 1 and 4, but do not give any theoretical causal relationship,
then their hypotheses can be viewed as “experiential.” Of course, if students provide
a theoretical causal relationship in their hypotheses based on their background
knowledge, these hypotheses would be “theoretical.”
In summary, according to the findings from this study, a scientific inquiry activity
consisting of four steps for encouraging students’ ability to generate a scientific
explanatory hypothesis to explain the novel or conflicting phenomena is presented.
To achieve this, the important points are to let students search for hypotheses in their
background knowledge or other related experiences rather than in the phenomena to
be explained itself, use similarity-based reasoning to select or choose appropriate
information required to explain the phenomena from a wide range of background
knowledge or experience, and attempt to provide causal explanation, even if it is
tentative, between the phenomena and the information selected from their background knowledge, rather than describing the characteristics of the phenomena.
Conclusion and Implications for Conceptual Change
Although the results of this study have some limitations, largely due to the small
number of subjects, three types of hypotheses suggested by students can be identified - theoretical, experiential, and auxiliary hypothesis (see Table 3)—and could
model the processes of generating each type of explanatory hypothesis.
As mentioned earlier, conflicting evidence alone is not sufficient when changing
prior alternative conceptions, because when students explore the conflicting evidence
alone and attempt to find the reason of such anomaly in the conflicting evidence itself,
they only modified their protective belt and preserved their prior ideas while suggesting
an auxiliary hypothesis. Therefore, the generation of explanatory hypothesis—theoretical or experiential—can be said to be essential for discarding old misconceptions.
In this study, it is found that the background knowledge played a particularly
important role in generating a new theoretical hypothesis involving the theoretical
causal relationship, while displacing prior ideas. In this case, similarity-based reasoning is useful in connecting the background knowledge and the conflicting phenomena to be explained. Even though some students did not have the necessary
Table 3.
Major features of three types of explanatory hypotheses
Type of
hypothesis
Space searched
for hypothesis
Causal
relationship
Reasoning
Prior idea
Auxiliary
Target
Experiment (TE)
Background
Knowledge (BK)
Clue Experiments
(CEs)
No theoretical
casual relationship
Theoretical casual
relationship
No theoretical
casual relationship
No similarity-based
reasoning
Similarity-based reasoning
between BK and TE
Similarity-based reasoning
between CEs and TE
Preserved
Theoretical
Experiential
Displaced
Displaced
488 J. Park
background knowledge, by virtue of the relevant experiences, they could generate a
new experiential hypothesis using similarity-based reasoning between the relevant
experiences and the conflicting phenomena.
Darden (1992) notes that one of the general issues of the change and growth of
scientific knowledge is to find strategies for reasoning in theory change. Chi (1992)
also emphasized the need to understand which triggering factors could lead students
to realize the anomalies to be resolved. Park and Pak (1997) argued that, to stimulate
student’s cognitive conflict, students should be able to discriminate evidence from
their own ideas and recognize whether or not the evidence is available to support or
disprove their own idea. Park and Kim (1998) observed that cognitive effort through
a higher level of scientific inquiry skills helped students’ conceptual change. That is,
students were more apt to change their prior ideas when they used a higher-level
inquiry skill (e.g., control of variables) compared with a basic inquiry skill (e.g.,
observation). Based on the theoretical assumption that scientific explanations have a
deductive logical structure, Park and Han (2002) used a Deductive Explanation Task
as a strategy to help students recognize cognitive conflict and to resolve it—the Deductive Explanation Task was observed as being useful for conceptual change.
In this paper, similarity-based reasoning is suggested as another potential strategy
for effective conceptual change. Generally, the model of conceptual change is described
as composed of four stages: recognition of prior idea, cognitive conflict, resolution of
conflict, and recognition of the modified idea. Similarity-based reasoning can be
applied to the third stage of conceptual change. To encourage this reasoning, various
teaching strategies need to be developed. As mentioned earlier, Clement’s bridging
analogy strategy and a sample of an activity for teaching inquiry skill of generating a
new hypothesis (Figure 10) can also be used for encouraging students to use similaritybased reasoning. It is hoped that other useful strategies using similarity-based reasoning
can be developed and applied for teaching conceptual change in classroom learning.
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