The moon has no gravity: examples of idea-mixing in explanations of physical processes

Abstract

This paper presents a discussion of the role of student alternative conceptions in learning, and the ways in which non-scientific ideas can influence the acquisition of scientific models. Sample interviews with students provide a window into the role that prior knowledge plays on the development of ideas within the general adult public, and particularly the ways in which instruction can interact with this prior knowledge. We find evidence for a variety of ways in which students mix scientific and non-scientific ideas within geoscience. This work is in alignment with prior work on student conceptual understanding, and further supports the idea that lecturers must pay careful attention to prior knowledge when presenting new theories, models or paradigms. We conclude with suggestions for instructional approaches which are useful for uncovering students' prior knowledge.

Introduction

The role of students' conceptions in the learning process is a growing area of research in geoscience education and geocognition. This is spurred in part by examples set in other fields (e.g., physics; Slotta et al., 1995), and the growing importance of natural hazards and climate change in societal discourse. Both qualitative (e.g. Dove et al., 1999) and quantitative approaches (e.g. Black, 2005; Libarkin and Anderson, 2005) have been applied to investigating the conceptions held by novices. Of particular significance are those which explore conceptual understanding in general (e.g. Chi et al., 1994), the unique characteristics of alternative conceptions in geoscience (e.g. Trend, 2000), and the role that particular instructional interventions can have on student conceptual understanding (e.g. Elkins and Elkins, 2007).

Individuals, including experts, can hold multiple conceptual models simultaneously (Lewis and Linn, 1994). It is therefore important to make explicit the models held by those we are teaching in order to facilitate conceptual change, i.e. to help move students toward ways of thinking that are considered acceptable by the scientific community. In this paper, we present examples of mixed ideas that students hold about scientific and geoscientific concepts. We then consider the ways in which different pedagogical approaches useful for uncovering student ideas, such as those described in Libarkin (2006), could be used to help students move beyond mixed ideas towards conceptual change.

Methods

We examined a subset of interviews that had previously been conducted with students enrolled at a range of U.S. institutions. While a subset of these interviews has been used to understand the general state of student alternative conceptions (Libarkin et al., 2005; Truscott et al., 2006), we have not previously considered how these conceptions interact with instruction. Interview data presented here were collected from students enrolled at either a large public, four-year university in the US mid-west, or a two-year US community college in the northwest. These students were non-majors aged between 18 and 22 years. These would be broadly equivalent to UK students studying non- science disciplines, or to students entering geoscience from non-scientific backgrounds. We do not present a comprehensive analysis of these interviews, but rather consider exemplars that are useful for illustrating the role that mixing of ideas can have on student thinking. These data are representative of idea-mixing that we have observed across many U.S. institutions.

Examples of idea-mixing

The following extracts from student interviews illustrate the role that mixing of ideas can play in producing, encouraging, or buoying alternative conceptions and models of Earth phenomena. We have chosen this random sample of responses to represent differing student backgrounds, and a diversity of scientific concepts. Responses have been categorized to highlight some of the underlying characteristics of idea-mixing.

Category 1. Mixing from language misuse

Some mixing of ideas results from a simple misunderstanding of underlying scientific language. The interference with learning of colloquial terms that can also have scientific meaning is documented (e.g., Durkin and Shire, 1991). An example of an alternative conception that emerges from a language misuse can be seen in the following interview. This student, enrolled at a two-year U.S. college, had previously conveyed a sense that erosion occurs on other planets:

Interviewer: …”what do you think is the most important process on Mars, say, for erosion?”

Student: “I don't know, since there's no real atmosphere as we know it, at least that's what they say, I don't know how much proof they've got yet, but … usually wind and rain is from our atmosphere but there would be I guess some kind of a solar wind, … which would cause dust storms whatever … I guess getting hit by debris has got to wear down things.”

This student recognizes that wind is an erosional agent, understands that wind is an atmospheric process, and has heard that Mars lacks an atmosphere. His assumption that Mars has no atmosphere, rather than a thinner atmosphere than on Earth, seems to lead to a dissonance in how erosion can occur. The use of the term ‘solar wind’ to reconcile this dissonance results in a model for erosion on Mars that is conceptually confused.

Category 2. Mixing due to ambiguity in language

As seen above, scientific language can be easily misunderstood if it resembles common language. A related mixing of ideas can occur when the same language is used to describe relatively different phenomena. In the exchange below, a student, enrolled at a large, public four-year US university, is conflating the notions of ‘warm’ climate and ‘warm’ rock. In essence, use of the same common term by scientists to describe very different temperature regimes has produced an inaccurate model of the role of climate in volcano formation:

Interviewer: “Take that pen and mark with an X [on a map] anywhere that you think that a volcano would be…”

Student: “I think there are some out here in the ocean. But, I think they are more clustered around the equator because it's warmer there.”

Additional probing of the student's response would have been helpful to provide an understanding of why warmth is an important concept for locating volcanoes. Although only supposition, we deduce from this interview and from similar exchanges with other students that the relative difference between a ‘warm climate” and a “warm volcano” is not understood. ‘Warm’ is such a familiar concept to some students that the context within which the adjective is used (e.g., volcano versus climate) becomes lost. In these cases, the inexactness of the ‘warm’ description results in students building a false equivalence, and then extending this into building faulty models and rationales.

Category 3. Mixing of scientific concepts to form alternative conceptions

The mixing of correct ideas with alternative conceptions is a very common practice that results in inaccurate models of Earth phenomena. In addition, students may also hold a simple alternative conception that they can use as evidence for the correctness of their inaccurate models. In the exchange below, a student, enrolled at a two-year college, is prompted to explain gravity in relation to Figure 1. During this explanation, the student blends concepts, such as Earth's rotation and magnetism, which have little to do with gravity itself.

Interviewer: “… you talked about gravitational attraction, what is that?”

Student: “That's the force exerted on the surface of the Earth due from its rotation and it… has a magnetic pull force inside of it, I don't know with the spinning, I think… ”

Interviewer: “So you said about the rotation…you talked about a magnetic pull … how do those two things relate to gravity?”

Student: “Well, they're basically what keeps gravity in check. Without either of those things we probably wouldn't have, we'd have no gravity on Earth…”

Figure 1 The student was asked to respond to the following open-ended question: “Pretend that a tunnel was dug all of the way through the Earth. Imagine that a person standing at the surface holds a rock and drops it. Draw a line from the person's hand showing the entire path taken by the rock.” After Asghar & Libarkin (2010).

As we can see, the student provides a simple model for the importance of magnetism and rotation on gravity. From this, we can interpret that the student has been exposed to concepts of gravity and magnetism, and rightly recognises that both forces are active on Earth. Conceptual understanding about these forces, however, is clearly not well developed in the student, leading to a mixing of concepts and resulting in the development of an incorrect model.

Category 4. Reasoning from an alternative conception to confirm a model

One of the most interesting phenomena observed in student interviews is the sophisticated reasoning that students can use to confirm incorrect ideas or models. In a continuation of the interview from Category three above, the student provides a rationale for the importance of magnetism in gravitational attraction; this rationale is based on an alternative conception about the lack of gravity on the moon.

Interviewer: “if the Earth didn't have that [magnetic pull], would we have gravity?”

Student: “I don't think so. No.”

Interviewer: “Okay. Do, do you know why… or is it just an idea? “

Student: “Well it's, I guess it's kind of just an, a concept that was presented to me in geology and so because like the moon, you know, it doesn't, it rotates, it kind of rotates in a direction but it doesn't have the, it doesn't have the magnetic core like the Earth does and that's probably why it doesn't have any gravity.”

In essence, this student has been able to use a common alternative conception, the idea that the moon has no gravity, to buoy a model of gravitational attraction resulting from Earth's rotation and magnetism. First, the student incorrectly states that the moon has no rotation, another common alternative conception, and then correctly states that the moon does not have a magnetic core. Together, these provide the basis for a rationale that these phenomena, existing on Earth, are responsible for Earth's gravitational field.

Implications and suggestions for instruction

Libarkin (2006) presented a synthesis of approaches that can be used to uncover alternative conceptions. Here, we consider the role that each approach may play in mixing of ideas as well as steps lecturers can take to mitigate the development of mixed, and non-scientific, models. We primarily follow the simplified categorization used by Libarkin (2006) as we have found that it aligns well with actual practice in the university-level classroom.

Short questions. Brief written responses to questions posed prior to instruction can give insight into the nature of student familiarity, and/or misunderstanding, of a concept (e.g. Bradbeer et al., 2004; Tóth and Ludányi, 2007). This method is useful for collecting information about conceptual understandings from groups of students (Minasian-Batmanian et al., 2006), but does not allow for further probing of responses.

Conversations and interviews. Verbal exploration of students' conceptual understandings, e.g. through formal interviews as reported here or through classroom-based discussions, can enable lecturers to gain a deeper insight into the source of individuals' ideas and beliefs about geoscientific concepts. while this approach enables the lecturer to probe for further detail and explanation, it can be time-consuming relative to written responses.

Thought experiments. More complex responses can be collected from students when lecturers are interested in gaining a better understanding of the relationship of alternative conceptions to reasoning. Kortz et al. (2008) describe the use of Lecture Tutorials to qualitatively identify and explore students' alternative conceptions. This approach involves students working in small groups to complete interactive worksheets following a brief introductory lecture. Quantitative approaches are appropriate when the range of student ideas is fairly well-known from existing research or prior instructional experience. McConnell et al., (2006) describe the use of higher-order multiple choice questions, known as ConcepTests, to increase student engagement and improve understanding of specific topics. One possible negative outcome of this approach is that forcing students to think about unfamiliar conceptions could potentially lead them to develop confused models, such as those described above, although no research currently exists to support or refute this suggestion.

Free-hand and augmented drawings. Sketches, realistic drawings, and schematic diagrams provide excellent opportunities for students to display their deeper understanding of scientific models and natural processes (e.g. Gobert, 2000; Sibley, 2005). Not all students are adept at expressing themselves through drawing, however, so these can easily be misinterpreted. To overcome this, it is common for drawings to be combined with some kind of verbal discussion in order to explore students' thinking about a particular concept.

Conclusions

This paper presents a brief overview of the ways in which student ideas can interact to produce incorrect mental models. In the US and elsewhere, the investigation of student conceptions of geoscientific phenomena is a highly active line of research, and one that has yielded some significant insights into the mental models held by novice learners. Although the UK has made some contribution to this body of research (e.g. Dove et al., 1999; Trend, 2000; Blake, 2004), it has yet to fully engage in this type of work across all levels of education. The outcomes from conceptions research can be used to inform curriculum development and undergraduate instruction, particularly with regard to helping students acquire scientifically valid ways of thinking about geoscience.

Opportunities for geoscience practitioners in the UK and US to interact occur at national meetings in both countries, e.g. at the Geological Society of America (GSA) and GEES Subject Centre conferences. These interactions are invaluable for exchange of pedagogical ideas and comparison of student conceptual understanding and alternative conceptions. New online opportunities for sharing of teaching resources (e.g., Science Education Resource Center; http://serc.carleton.edu) and assessing student thinking (e.g., Geoscience Concept Inventory WebCenter; http://gci.lite.msu) provide further opportunity for cross-cultural communication and engagement. Collectively, we have the potential to enhance student learning in undergraduate geoscience courses on both sides of the ocean.

Glossary
Conceptions	=	Ideas and understandings founded in experience
Alternative conceptions	=	Conceptions held by learners which conflict with explanations accepted by the scientific community
Novices	=	Individuals who are new to a particular area of academic study
Experts	=	Individuals with significant training in, or experience of solving problems in, a particular area of academic study