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Can Students Learn from Lecture Role and Place of Interactive Demonstrations? The Lecture Experiments in Large Introductory Science Courses By Marina Milner-Bolotin, Andrzej Kotlicki, and Georg Rieger
In this article we describe a case study of interactive lecture experiments in a large introductory physics course. The impact of this pedagogy on student learning and motivation is also discussed.
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here is little doubt that wellperformed lecture demonstrations play an important role in science teaching (Straits and Wilke 2006): for many students, exciting demonstrations are what keep them interested and motivated. The demonstrations also help the instructor to change the pace of the lecture and prevent students from losing their concentration; the average attention span for college students is about 15–20 Marina Milner-Bolotin (milnerm@phas. ubc.ca) is a research associate and Andrzej Kotlicki and Georg Rieger are lecturers in the Department of Physics and Astronomy at the University of British Columbia in Vancouver.
minutes (Middendorf and Kalish 1996). There is a lot of discussion about different ways of presenting the demonstrations and their effectiveness in promoting student understanding of science concepts. As much as students enjoy the demonstrations, there is ample evidence that just seeing a demonstration is insufficient for the majority of them (Julian 1995; Roth et al. 1997; Laws 1998; Crouch et al. 2004). Contradictory to a common belief that seeing a demonstration makes students understand or at least remember the phenomena, many science instructors have documented that after seeing a demonstration, the majority of students comes away with an incorrect interpretation of what they saw,
and may even “remember” witnessing a phenomenon that didn’t occur during the demonstration. We began studying this effect during the fall semester of 2004. At that time we showed three groups of 250 students in an introductory physics class a system consisting of a pendulum bob (a mass on a string) connected to a spring scale used to measure the tension in a string during the swing (Figure 1). The students were asked then to observe the reading of the scale in two situations: (1) when the pendulum bob was at rest; and (2) while the pendulum was swinging. It is worth mentioning that this experiment focuses on a rather difficult concept for the majority JANUARY/FEBRUARY 2007
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of students because it requires a simultaneous application of a few concepts: Newton’s laws (applied to the situation where the forces change both in magnitude and in direction), circular motion, and the concept of string tension. During the instructor-centered discussion of the phenomenon, we emphasized that in the first case, the scale reading corresponded to the weight of the pendulum, which was equal in magnitude to the tension in the string. In the second case, the reading of the scale varied, corresponding to varying tension in the string. The tension in the string was the highest at the lowest point of the swing, when the speed of the pendulum was also at its highest. This phenomenon was explained using Newton’s second law and a circular-motion model. A few weeks later, students had a midterm exam that included the multiple-choice problem shown in Figure 2. Because the weight of the pendulum is 2 N, solving the problem does not require any calculation: only the correct answer (E) is larger than 2 N. Nevertheless, only 25% of students who were exposed to the lecture demonstration described above were able to answer this question correctly, and approximately 59% chose an incorrect response: (D). Students’ choices indicate that they still believed that the tension in the string must equal the weight of the pendulum, contrary to the results of the lecture demonstration. To make sure that this was indeed their thinking, we conducted interviews with students. Many of them attested that they clearly remembered the demonstration showing that the tension in the string had the same value as the weight of the bob. Amazingly, they remembered not what they saw, but what they expected to see. Despite the instructor’s attempt to use this demonstration to clarify a difficult concept, the demonstration only suppor ted students’ inaccurate understand46
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ing of physics phenomena. One is tempted to blame the instructor for ineffective teaching; however, the research-based evidence indicates that the problem lies deeper than that. Students who have a chance to observe physics demonstrations during lectures (accompanied by the instructor’s explanations) without any further activity on students’ part show very little learning of the
Amazingly, students remembered not what they saw, but what they expected to see. underlying science concepts. The rate of correct responses to the conceptual questions illustrated by the demonstrations adjusted to a control group who had no demonstrations shown to them varied between 8% and 12% (Crouch et al. 2004). Our experience confirms what other instructors have discovered— that students don’t gain thorough conceptual understanding just from observing a demonstration. On the other hand, students who had a chance to predict an outcome of a demonstration prior to seeing the demonstration achieved a significantly higher success rate of 25%–35%. Furthermore, students who had the opportunity to make a prediction, discuss it with peers, and only then observe the demonstration, were found to be getting the most out of this learning experi-
ence—their rate of correct responses was higher than 50%. These and many other similar research f indings inspired a significant number of physics-education researchers and science instructors to reconsider the role and place of science demonstrations in introductory college courses. For instance, a researcher from the Activity-Based Physics Group (Laws 1998; Sokoloff, Thornton, and Laws 2004) introduced Interactive Lecture Demonstrations (ILD). This demonstration technique requires students to make a prediction before seeing a demonstration and write it down on a specially prepared worksheet provided at the beginning of the lecture. In variations of this pedagogical method, students can do the prediction individually or they can discuss it with peers. Then students observe the demonstration and reflect on how the result confirms or fails to confirm their initial prediction. The aim of this method is to elicit students’ misconceptions (sometimes referred to as prior concepts) about physics phenomena and create a cognitive conflict, which will presumably help them get rid of these misconceptions and replace them with the correct concepts underlying the physics phenomenon under consideration (Clement 1982; Lawrenz 1986; Hunt and Minstrell 1994; Stephans 1996). If the pendulum problem discussed above were introduced as an ILD, students would have been asked to make a prediction about the tension in the string and write it down, observe the demonstration, and only then to
TABLE 1 Interactive Lecture Experiments (ILEs) implemented during the fall semester of 2005 (750 students). Title
Topic
Basketball shot
Two-dimensional kinematics (example)
Ball toss out
Two-dimensional kinematics
Pendulum
Energy conservation, circular motion
Who said pigs don’t fly!
Circular motion: conical pendulum
reflect (individually or though group discussion) on how accurately their prediction described the observed phenomenon. While instructors who use the ILD method have shown its superiority over traditional lecture demonstration methods, the negative emotional impact of cognitive conflict on students’ confidence cannot be ignored. In large science classes for non-physics or even nonscience majors, the issue of motivation bears an additional weight: students have to learn to self-regulate their learning, and motivation is a stepping stone in this process (Pintrich 1999). We therefore attempted to develop an approach that has the same benefits as the ILD, but avoids putting students in a threatening learning environment.
Interactive Lecture Experiments
At the University of British Columbia we developed and piloted (MilnerBolotin 2005) a different technique for presenting lecture demonstrations called Interactive Lecture Experiments (ILE). The main difference between the ILDs and ILEs is that we are not trying to create a cognitive conflict in students’ minds. Instead, we are helping students learn to make careful observations (seeing what is happening rather than seeing what they think is happening), work with peers to explain the observations using their science knowledge, and test their explanaFIGURE 1 Tension in the pendulum demonstration.
tions using additional experiments (Etkina and Heuvelen 2001; Etkina et al. 2002). The ILE technique is described in Figure 3. It consists of five stages comprising every ILE cycle: demonstration; data collection (by the instructor during the lecture) and sharing the data with students via the web; data analysis by students outside of the classroom while working in groups of three or four; in-class discussion of experimental results and summary of the data analysis; and problem solving with concepts discussed in the ILE during tutorials or in homework assignments.
I: Demonstration stage (in-class activity)
Students are shown an experimental setup during the lecture. The instructor discusses physics concepts and phenomena illuminated by it without going into specific details. For instance, in the case of the pendulum, a swinging pendulum connected to a scale is shown. The scale reading during the pendulum’s oscillation is demonstrated to students without going into quantitative calculations. The concepts of string tension, weight of the pendulum, Newton’s second law, energy conservation, and circular motion are used to describe the situation qualitatively. This discussion helps students start independent investigations of the phenomenon, which they are asked to conduct in small groups at home, using a textbook, lecture notes, online resources, etc.
II: Data collection and sharing (performed by the instructor)
The same experiment is either videotaped prior to the lecture and shown during class or is demonstrated as part of the lecture. Data from the experiment are collected using a computer probe such as Logger Pro from Vernier Software (www.vernier.com). The data are uploaded to the web and shared with students. Specific questions about data analysis are also given to students (Milner-Bolotin 2005) to help direct their investigations.
III: Data analysis (performed by students outside the classroom)
Students are asked to download from the web the video clip of the experiment or the collected data and to analyze it outside of the classroom while working with peers. This is considered to be a homework assignment performed in small groups using Logger Pro software (see Acknowledgments). During the analysis, students are asked specific questions, which are indicative of their conceptual understanding as well as their ability to support qualitative analysis with quantitative results. For instance, in the case of the swinging pendulum, the mass of the pendulum is given to students and the initial height of the pendulum could easily be measured from the video clip. Students are asked to calculate the tension in the string at its lowest point and compare the obtained value to the readings of the scale. (Visit www.physics.ubc.ca/~year1lab/ p100/LectureLabs/lectureLabs.html to view all of the authors’ interactive experiments.)
IV: In-class discussion
Students bring results of their analysis to class. During the all-class discussion, students use electronic transmitters, often called clickers (Duncan 2005), to submit their answers to the questions asked in the experiments. In addition, each group also submits a brief written report of their analysis. The instructor asks students to summarize the results of the data analysis, which are then shared with the entire class. For instance, one of the most important results of this experiment is that the tension in the string can be smaller or larger than the weight of the pendulum, depending on the magnitude and direction of the acceleration of the pendulum.
V: Problem solving involving concepts discussed in the ILE
During this activity, which starts in class and extends to the homework assignment, students are asked JANUARY/FEBRUARY 2007
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questions requiring application of the concepts learned in the Interactive Lecture Experiments to new situations. For example, students are asked to analyze various situations in which two opposing forces add up to a different value, due to the fact that one of them varies in magnitude while the other one remains constant. One example is a person standing on a scale in an elevator accelerating at various rates: the person’s weight remains constant while the normal force the scale exerts on a person (often referred to as apparent weight) changes. An alternative example is using a force plate (a special scale connected to a force probe) to measure the normal force a person exerts on a scale during squatting. (A video of this demonstration is available at www. vernier.com.)
Results
During the fall term of 2005, we implemented four ILEs (Table 1). The first ILE was performed, discussed, and analyzed by the instructor in class to help students get acquainted with the method and with the Logger Pro software. The other three ILEs were performed by the instructor and analyzed by students according to the ILE cycle described in Figure 3. It is not surprising that in order to benefit from the ILE and to be able to perform the data analysis, students had to learn how to use the Logger Pro software. To help students get started, we created a course-specific Logger Pro manual, which was available on the lab website. Our experience indicates that within a few weeks, most students were able to master the basic skills of Logger Pro and become comfortable with it. However, we also found that students’ difficulties in performing the data analysis stemmed mainly from their poor conceptual understanding of the basic mathematical concepts related to curve fitting, descriptions of various functions, and simple 48
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statistical analysis. For instance, the concept of fitting the data with a line or a curve was not obvious to many students. These technical and procedural diff iculties were reflected in the first midterm survey (one month into the term), in which students were asked to rate the effectiveness of the ILE. Only 52% of students surveyed found the ILE helpful. As the term progressed and students became more comfortable with the concept of video analysis and with the Logger Pro applications, their attitudes toward the ILEs shifted considerably. In the second survey conducted two months into the term, more than 78% of students said that they found ILEs to be helpful or very helpful. It is worth mentioning that students found the ILEs as helpful or sometimes more helpful than hands-on labs. These findings corroborate the findings of the Physics Education Technology Research Group at the University of Colorado at Boulder, suggesting that virtual labs based on the finding of the physics education research can
be more effective than traditional hands-on labs (Finkelstein et al. 2005) . During the midterm exam in the fall of 2005 we asked students the same pendulum question (Figure 1). More than half of students who were exposed to the ILE answered this question correctly. While it was obviously not a perfect outcome, we saw a significant improvement compared to the previous year (fall term of 2004). This favorable shift had been also reflected in the improved quality of ILE write-ups submitted by students as group mini-projects. Moreover, during the midterm and final exams, we observed improvements in students’ ability to explain and solve traditional physics problems. Students’ written responses to the open-ended problems in the final exam reflected this. These preliminary observations suggest that an opportunity to apply physics concepts qualitatively and quantitatively to everyday life phenomena via ILEs was a very valuable experience for many of our students. However a more rigorous
FIGURE 2 Tension in a pendulum’s string exam problem.
A 0.2-kg pendulum bob is attached to a string 1.2 m long. The bob is released at the point A as shown in the picture. The tension in the string as the bob passes its lowest position is about (use g = 10 m/s2): (A) 0.00 N
(B) 0.70 N
( C) 1.30 N
(D) 2.00 N
(E) 2.70 N
FIGURE 3 Interactive Lecture– Experiment cycle.
University of British Columbia. We would also like to thank Fran Bates, Robert Kehoe, Joe O’Connor, Jon Nakane, and Kelly McPhee for their help in designing and testing the first versions of the interactive lecture experiments. We would like to thank Joel A. Bryan from the Center for Math and Science Education at Texas A&M University for allowing us to use the video clips published on the center’s website: www.science.tamu. edu/CMSE/videoanalysis/index. htm, and Douglas Brown for creating and sharing the Tracker video analysis resource: www.cabrillo. edu/~dbrown/tracker. We would like to thank Vernier Software and Technology (www.vernier.com) for allowing us to make the Logger Pro software available to students without any additional cost. References
study is required to investigate the specific effects of ILE pedagogy on students’ academic achievement, attitudes, and motivations. A study aimed at exploring the effects of ILEs on students’ academic achievement, attitudes and motivations is currently underway with 800 undergraduates taking an introductory physics course (Physics 100) at the University of British Columbia. The data for the study will be collected by December of 2006 and the results will be reported as soon as they become available. Based on our recent experiences, we strongly believe that ILEs can be implemented in any science class where lecture demonstrations, coupled with modern technology, can be used for data collection and analysis. ■ Acknowledgments
This work has been generously supported by the Teaching and Learning Enhancement Fund (TLEF) at the
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