«Using Bridging Analogies and Anchoring Intuitions to Deal with Students’ Preconceptions in Physics John Clement ScientiJic Reasoning Research ...»
JOURNAL OF RESEARCH IN SCIENCE TEACHING VOL. 30, NO. 10, PP. 1241-1257 (1993)
Using Bridging Analogies and Anchoring Intuitions to Deal with Students’
Preconceptions in Physics
ScientiJic Reasoning Research Institute, University o Massachusetts,
Amherst, Massachusetts 01003
Lessons were designed to deal with students’ alternative conceptions in three areas of mechanics:
static normal forces, frictional forces, and Newton’s third law for moving objects. Instructional techniques such as class discussions of the validity of an analogy between a target problem and an intuitive anchoring example, and forming a structured chain of intermediate bridging analogies were used. There were large differences in pre-posttest gains in favor of the experimental group. In formulating a model of learning processes that can explain these results, it is argued that (a) the lessons have a more complex structure than a simple model of analogy use; (b) rational methods using analogy and other plausible reasoning processes that are neither proof based nor directly empirical can play a very important role in science instruction; (c) much more effort than is usually allocated should be focused on helping students to make sense of an analogy; and (d) researchers and curriculum developers should be focusing at least as much attention on students’ useful prior knowledge as they are on students’ alternative conceptions.
This article discusses the use of analogies and other instructional strategies in dealing with students’ preconceptions in physics. In order to discuss students’ conceptions and their relationship to instructional strategies, it is important to clarify some of the terms to be used. Because the context here is instructional strategy development, the term preconception will be used to mean a conception in a certain area that is present in a student prior to instruction. It is important to emphasize that not all preconceptions are misconceptions. The lessons to be discussed here are also based on preconceptions that are largely in agreement with currently accepted theory.
Here these will be termed anchoring conceptions (Clement, Brown, & Zietsman, 1989).
Alternative conceptions (misconceptions) are used here for conceptions that can conflict with currently accepted scientific theory. There has been some controversy over whether to call these misconceptions, alternative conceptions, or something else. A potential problem with the term misconception is that it might suggest a negative connotation with respect to the worth of the student’s self-constructed ideas and thought processes. Such conceptions should be respected as creative constructions of the individual, and in some cases they are successful adaptations to practical situations in the world. The problem with the term alternative conception is that it can be taken to mean that all ideas are equally useful in all contexts, which is not true. In some contexts naive subjects can have maladaptive beliefs, such as misconceptions about disease transmission.
0 1993 by the National Association for Research in Science Teaching Published by John Wiley & Sons, Inc. CCC 0022-4308/93/ 101241- 17
CLEMENTProbably the most important need is to define precisely the terms that one uses. Here I suggest that a useful definition for both of the terms misconception and alternative conception (treated here as synonyms) is the one I have used in the past for misconception: a conception that can conflict with currently accepted physical theory. This definition avoids implying that the expert has found truths with absolute certainty or that the naive student’s ideas are worthless and unimprovable. In this article I will favor the term alternative conception.* In the context of a course on Newtonian mechanics, student errors or correct answers are defined in a similarly neutral way with respect to their agreement with Newtonian theory.
By changing an alternative conception or conceptual change here I mean overcoming the dominance of an alternative conception in inappropriate situations in some way; thus it could mean modify the domain of, displace, modify and improve, replace, or suppress a conception, depending on what is most appropriate.
The Problem of Alternative Conceptions There is now considerable evidence that students in physics courses experience significant conceptual difficulties at a qualitative level in addition to the challenge of learning quantitative concepts. Patterns in the errors on qualitative problems indicate that the errors are not random.
Along with interview data, they suggest that students are not simply failing to learn new material, but have alternative conceptions about it. Pretests and interviews given prior to the course show some of the same error patterns and indicate that students are entering courses with alternative preconceptions. Collected evidence for these findings can be found in Driver and Easley (1978), Driver and Erikson (1983), McDermott (1984), Pfundt and Duit (1991), Helm and Novak (1983), and Novak (1987), among others. Similar data taken after courses indicate that some of these preconceptions do not change much and constitute persistent barriers to achieving conceptual understanding (Minstrell, 1984). This can even occur for large numbers of students in calculus-based college physics courses, even though they may be proficient at the use of physics formulas (Clement, 1983; Halloun & Hestenes, 1985). This indicates that courses need to place increased emphasis on dealing with alternative conceptions.
Deep Seatedness. It is clear that some alternative preconceptions are more deep-seated than others. As Chaiklin and Roth (1986) point out, incorrect answers to diagnostic problems may not always reflect deeply held preconceptions, because students are willing to use beliefs they are uncertain about in problem solving. However, there are several different types of evidence indicating that some alternative preconceptions are deep-seated, in addition to the prepostcourse tests cited above. Confidence measures provide some evidence: Brown and Clement (1987) found that students indicated they were fairly confident in their incorrect answers on a set of qualitative problems in the area of Newton’s third law of “equal and opposite forces” after taking high school physics. Other indications of deep-seatedness include spontaneous expressions of conviction in interviews, resistance observed during tutoring (Brown & Clement, 1989), and historical parallels to students’ alternative conceptions (Clement, 1982; Steinberg, Brown, & Clement, 1990; Wiser & Carey, 1983). The latter indicate that the students are in good company; Westfall ( 1980), in his extensive, historical-cognitive biography, interprets Newton’s records as showing how certain persistent preconceptions, including impetus and centrifugal force, were mutually supporting and showing that they held Newton back for up to 20 years before he was able to finish the Principia.
A few initial attempts to deal with students’ alternative conceptions in physics have met with mixed but in some cases encouraging success (Brown, 1987; Halloun & Hestenes, 1985;
BRIDGING ANALOGIES AND ANCHORING INTUITIONSMcDermott, 1984; Minstrell, 1982) and researchers are beginning to formulate a variety of strategies (Scot, Asoko, & Driver, 1992). However, studies of in-depth interventions in specific content areas are needed in order to assess the different strategies being proposed.
Teaching Strategy Used in this Study The method used in this study for helping students deal with persistent alternative conceptions attempts to have students build up their understanding at a qualitative, intuitive level before mastering quantitative principles. It also encourages students to become aware of their own alternative conceptions, to actively criticize them, and to develop new conceptions.
The technique can be illustrated by describing a lesson used to address the alternative conception of static objects U S barriers that cannot exert forces. The classic target problem in this case is the question of whether a table exerts an upward force on a book placed on the table.
Observations from classroom discussions and tutoring interviews indicate that many students believe that static objects such as the table are rigid barriers that cannot exert forces. In a diagnostic test, 76% of a sample of 112 high school students indicated that a table does not push up on a book lying at rest on it. (These were chemistry and biology students who would be eligible to take physics in the following year.) On the other hand, 96% of these students believed that a spring pushes up on one’s hand when the hand is pushing down on the spring. For physicists, these two beliefs are incompatible because they see the two situations as equivalent.
diSessa (1983) refers to the concept of springiness as a “phenomenological primitive” and describes acquiring skill in physics as depending on the evolution of such intuitions. The handon-the-spring situation is a useful starting point for instruction because it draws out an intuition from students that is largely in agreement with the physicist. For this reason it is called an anchoring example that draws out an anchoring conception. Such intuitions may be articulated or tacit.
A Strategy that Failed A reasonable strategy would be to present the hand-on-the-spring and the book-on-the-table problems to students and ask them if they are not indeed analogous. When students see that the table is analogous to a spring they should change their view of the book on the table situation.
Unfortunately, pilot tutoring interviews conducted by David Brown have indicated that this simple strategy does not often work. Instead, students typically say that the table is not at all the same as a spring-the table is rigid or dead, whereas the spring is capable of returning to its original position and pushing back-so the spring can exert a force, whereas the table cannot.
Thus there is a need for an additional effort to help students see how the analogy between the spring and the table can be valid. This effort fits with the more general plea of Posner, Strike, Hewson, and Gertzog (1982) to make science ideas plausible to students (e.g., having it make sense that tables push up) as well as comprehensible (knowing that tables push up). Minstrel1 (1982) has reported some success in using key examples in Socratic teaching for the book-onthe-table problem. In what follows we will build on his ideas by adding an explicit emphasis on anchoring intuitions, structural chains of analogies, and mechanistic models in such lessons.
Applying an Expert Learning Strategy Using Bridging Analogies The spontaneous use of analogies has been documented in think-aloud interviews with scientists (Clement, 1981, 1988), and with students (Clement, 1987). Experts have also been observed to use special patterns of analogical reasoning in order to stretch the domain of a key 1244 CLEMENT
analog example, confirm the validity of an analogy, and overcome a conceptual difficulty (Clement, 1986, 1989). It was conjecture that these patterns might be useful for overcoming conceptual difficulties in students as well. Examples of these patterns applied to the normal forces area are identifying salient features that are the same in the book and the spring; showing the existence of a conserving transformation between the book and the spring; and using a technique called bridging, described below.
Figure 1 shows a thin flexible board case used to help students determine that the analogy between the hand-on-the-spring anchor and the targeted book-on-the-table case is valid. The strategy of finding an intermediate third case that shares features with both the original case and the analogous case is termed a bridging analogy. Here, the idea of a book resting on a flexible board (case B) shares some features of the book on the table (case C) and some features of the hand on the spring (case A). The subject may then be convinced that A is analogous to B and that B is analogous to C with respect to the same important features, and thereby be convinced that A is analogous to C. Such bridges are not deductive arguments, but experts have been observed to use them as a powerful form of plausible reasoning (Clement, 1986). Presumably, this method works because it is easier to comprehend a close analogy than a distant one; the bridge divides the analogy into two smaller steps that are easier to comprehend than one large step.
Method In this study several lessons were constructed around the bridging-from-anchors strategy and tested against control groups to see whether progress could be made in areas where persistent alternative conceptions exist.
Sample Subjects were high school students taking a first-year physics course. The study involved three experimental-group teachers in two high schools and two control-group teachers in two other high schools. The experimental group consisted of 150 students and the control group contained 55 students. Experimental-group teachers participated in a 1-week workshop on the lessons during the summer in the pilot and experimental years.
Intervention Experimental lessons were constructed by a design team consisting of David Brown, Charles Camp, John Clement, John Kudukey, James Minstrell, Klaus Schultz, Melvin SteinBRIDGING ANALOGIES AND ANCHORING INTUITIONS
berg, and Valerie Veneman. The lessons were pilot tested for 1 year and revised on the basis of classroom observations. Updated versions of these lessons can be found as three of the nine units in Camp et al. (in press).
The experimental lessons sometimes used more than one intermediate bridging case; as shown in the concept outline of the lesson on static forces in Figure 2, a second bridging case of a book on a flexible foam pad was used. The analogies were not presented to the students in a lecture. During the lesson, the class compared each of the thought experiment examples in a discussion led by the teacher. As each case was introduced, the teacher challenged students to say why they believed that cases were similar or different and did not share the physicist’s view until near the end of the class.