Misconstruals or more? The interactions of orbit diagrams and explanations of the seasons

This paper examines a “misconstrual hypothesis” regarding diagrams of the Earth’s orbit around the sun and how middle school students explain the cause of the seasons. Drawing from 24 semistructured interviews, I present qualitative analyses of students’ explanations of why temperatures vary in summer and winter and how those are influenced by the elliptical shape of perspective drawings of the Earth’s orbit, common to many science textbooks. The results of the analysis suggest that diagram interpretation does not necessarily follow what has been often predicted in the literature and that conceptualizations can shift quite rapidly as different diagram features are noticed. A knowledge-in-pieces approach for understanding diagram interpretation is ultimately recommended through specific examples. Introduction The relationship between diagrammatic representations in textbooks and conceptual understanding in science has frequently been characterized as a problematic one (Holliday, 1985). While diagrams and technical figures are essential to the practices and knowing of science, several critiques have been put forth over the past decades about how diagrams that appear in canonical textbooks can be problematic for student learning (American Association for the Advancement of Science, 2002; Carvalho, Silva, & Clement, 2007; Kesidou & Roseman, 2002; Kikas, 1998; Wampler, 2002). In the most extreme cases, suggestions are made that specific classes of commonly appearing textbook diagrams will induce specific misconceptions that have been described in the science education literature (e.g., Cho, Kahle, & Nordland, 1985; Driver, Squires, Rushworth, & Wood-Robinson, 1994). This approach of conceptualizing diagrammatic representations as inducing specific and robust misconceptions as invoking what I term as a misconstrual hypothesis. The core of the hypothesis is that a fairly direct, causal relationship between external representation and mental representation exists. Astronomical and Earth Sciences have been an especially prime area for which the misconstrual hypothesis has been instantiated. Among the most famous predicted misconstruals involves perspective drawings of the earth’s orbit around the sun, which is thought to be induce a misconception of seasonal temperature variation resulting from a dramatically elongated orbit. This predicted misconstrual has had such tremendous intuitive appeal that it has appeared in the well-known video case study A Private Universe (Schneps & Sadler, 1988), in empirical studies of students’ misconceptions (Kikas, 1998), and even in a recent consensus report prepared by the national research council(Duschl, Schweingruber, & Shouse, 2007). Figure 1: Screen still from A Private Universe video as the suggestion is made in the voice-over that diagrams such as this lead to the common orbit-based misconception about the seasons. Yet, to date, little to no empirical investigation has been undertaken in order to determine, if indeed, that predicted relationship exists. Rhetorically, the misconstrual hypothesis has been invoked in critiques of curriculum or textbook images alone, or in studies of students’ alternative conceptions. But strong evidence that something like a perspective drawing of the Earth’s orbit leading to misconceptions about the causes of the seasons has been lacking. This paper seeks to address that absence through an empirical study of diagrammatic representations of the earth and sun and student conceptualizations of the causes of the seasons. I will present the results from a qualitative study (N=24) with middle school student who, at the time of the study, had no prior formal instruction about the seasons. These students each participated in think-aloud interpretations and semi-structured conceptual interviews with one of three randomly-assigned, commercially published textbook representations. Using this data, I will argue that a direct relationship between perspective depictions of the earth and sun are not clearly leading to the expected seasons misconceptualization. Rather, an entirely different and undocumented alternative conception is most frequently articulated, and then these are eventually adapted as students engage in closer inspection of the representation. Theoretical perspective The introductory language follows from studies of students’ mental models (Gentner & Stevens, 1983) and alternative conceptions (Driver, et al., 1994), and is intentional in that it motivates the work of this paper. Specifically, this paper examines a strongly implied (or at times, directly stated) relationship between diagrams and cognition that presumes relatively stable conceptualizations in the minds of students. As the empirical results will show, this is ultimately not the most generative theoretical framing, as there is far more fluidity to students’ explanations of scientific phenomena and a much more dynamic interaction between representation, conceptualization, and task context than is often assumed. In response to these results, I advocate for a Knowledge-in-Pieces perspective to characterizing the observed student science cognition (diSessa, 1988). According to a Knowledge-in-Pieces perspective, the underlying intuitive knowledge system is understood to be composed of a large number of individual elements of diverse form that interact and give rise to emergent explanations and accounts for scientific phenomena. Following a knowledge analysis approach (diSessa, 1993; Duncan, 2007; Sherin, 2001), I take specific excerpts of the interviews and dissect them in a fine grained manner to articulate the elements of knowledge that appear to be most active and involved in the generation of what are seemingly incorrect interpretations and explanations. By its nature, this is a challenging endeavor, as it is difficult to pinpoint when an element has been validly identified. However, I use the criteria of generativity and plausibility to make my case with the data excerpts. An additional move I make in this knowledge analysis is through analysis of not only the elements of knowledge that are active, but also the elements of the diagram which are attended to by the students. The assumption with orbit drawings is that the elliptical shape is the element in orbit diagrams receives immediate attention. However, as it turns out, there are far more features than that which are detected and considered by this sample of students. By characterizing the elements of the diagrammatic representation, I attempt to use the knowledge-in-pieces framework in a manner which is distributed both between the minds of students and with the physical representation itself (Martin & Schwartz, 2005). Data sources The data comprise of a corpus of video-recorded semi-structured interviews with 24 middle school students, grades 7 and 8, from three different schools located in or near a major Midwestern city. These students were all volunteers, from a range of academic abilities and backgrounds, who agreed to be interviewed individually by a university researcher during the student’s science class. Each interview spanned four different science topics and lasted between 45 minutes and one hour. The interviews required students to examine an isolated representation taken from a science textbook and think-aloud as they made sense of what was being shown to them. Following that think-aloud period, the students were then asked to explain a major scientific idea related to the diagram they were examining. For the earth’s orbit drawings, the students were asked what they believed caused seasonal temperature variation. Following that, each student was asked a standard set of questions in which he or she was to locate, by pointing, where the Earth would be in its orbit when it was hottest and coldest for the city they lived in, and then again for a city located in Australia. Half of the students in the sample were also asked, prior to viewing of the given diagram, to explain the cause of the seasons and locate the Earth in its orbit under the same city and temperature conditions through a drawing of their own creation, in order to establish a baseline. This baseline helped to establish that, beyond their teacher’s reports, that the students had not had pre-existing instruction about the cause of the seasons. Three diagrams from actual science textbooks were used and were randomly assigned for students to examine. These diagrams came out of a corpus of texts analyzed for a separate study on historical change in representation design in instructional materials (Lee, 2010). Two of these involved elliptical depictions of the earth’s orbit and one involved a circular depiction. Each student was only shown one of the orbit diagrams during their interview. Figure 2: Orbit diagrams used in this study. Results Lines and passages that referenced the cause of the seasons in the transcribed interviews were coded on the basis of four explanations emerged from the data and have been observed in other research (Atwood & Atwood, 1996; Sadler, 1987). They include the following: Explanation Illustration of explanation Seasons are because one hemisphere is facing the sun and the other is facing away. This explanation for the cause of the seasons involves designating the half of the earth that is closest to the sun as experiencing summer because it is facing and the side that is farther is experiencing winter. 1 Images from Principles of science (1979) by Heimler & Neill, published by Merrill, General Science (1989) by Watkins, et al., published by Harcourt, Brace, & Jovanovich, and You and science (1955) by Paul F. Brandwein, Alfred D. Beck, Leland G. Hollingworth, Anna E. Burgess, published by Harcout Brace Seasons are because the Earth is closer to or farther from the sun during its orbit. This explanation for the cause of the seasons is similar to and inclusive of the misconception documented by Sadler and others. The elongated orbit is