Supporting Students' Construction of Scientific Explanations Using Scaffolded Curriculum Materials and Assessments

We investigated the influence of scaffolding on students’ scientific explanations over an eightweek middle school chemistry unit. Students received a focal lesson on an explanation framework and then completed investigation sheets containing explanation component scaffolds over the unit. Students received one of two treatments: Continuous, involving detailed scaffolds, or Faded, involving less supportive scaffolds over time. We analyzed their investigation sheets and pretests and posttests. During the unit, students in the Continuous treatment provided stronger explanations than those in the Faded treatment. Yet on the posttest for the items without scaffolds, the Faded group gave stronger explanations than the Continuous group for certain content areas. Scaffolding Scientific Explanations 3 Supporting Students’ Construction of Scientific Explanations Using Scaffolded Curriculum Materials and Assessments Recent science reform efforts and standards documents advocate that students develop scientific inquiry practices (American Association for the Advancement of Science, 1993; National Research Council, 1996). “Learning science involves young people entering into a different way of thinking about and explaining the natural world; becoming socialized to a greater or lesser extent into the practices of the scientific community with its particular purposes, ways of seeing, and ways of supporting its knowledge claims” (Driver, Asoko, Leach, Mortimer, & Scott, 1994, p 8). One prominent inquiry practice in both the standards documents and research literature is the construction, analysis, and communication of scientific explanations. Although researchers cite explanations as important for classroom science, they are frequently omitted from classroom practice (Kuhn, 1993; Newton, Driver & Osborne 1999) and few research studies have examined the effectiveness of instructional practices in helping students construct explanations (Reznitskaya & Anderson, 2002). Our work focuses on an eight-week standards-based chemistry curriculum designed to support seventh grade students in their construction of scientific explanations. We investigated the effects of instructional and assessment scaffolds aimed at helping students construct scientific explanations. The Importance of Scientific Explanations Explanation construction is essential for science classroom practice for a variety of reasons. Research into scientists’ practices portrays a picture where scientists construct arguments or explanations including weighing evidence, interpreting text, and evaluating claims (Driver, Newton, & Osborne, 2000). Previous research in science education demonstrates that students who engage in explanation change or refine their image of science as well as enhance their understanding of the nature of science (Bell & Linn, 2000). Scientific explanations frame the goal of inquiry as understanding natural phenomenon, and articulating and convincing others of that understanding (Sandoval and Reiser, 1997). Lastly, constructing explanations can enhance students’ understandings of the science content (Driver, Newton & Osborne, 2000). A deep understanding of science content is characterized by the ability to explain phenomena (Barron et. al. 1998). The science standards documents also reflect the importance of incorporating explanation in students’ learning of science (American Association for the Advancement of Science, 1993; National Research Council, 1996). In particular, the National Research Council stresses the importance of explanation by including them in four of their five essential features of classroom inquiry (National Research Council, 2000). The table below (adapted from the National Research Council, 2000, p. 25) shows how explanations thread through many different aspects of classroom inquiry. Scaffolding Scientific Explanations 4 Table 1 Essential Features of Classroom Inquiry Bold added for emphasis Learners are engaged in scientifically oriented questions. Learners give priority to evidence, which allows them to develop and evaluate explanations that address scientifically oriented questions. Learners formulate explanations from evidence to address scientifically oriented questions. Learners evaluate their explanations in light of alternative explanations, particularly those reflecting scientific understanding. Learners communicate and justify their proposed explanations. Although the concept of scientific explanations permeates the research literature, there is not one accepted definition or framework for what counts as a scientific explanation. Furthermore, some researchers use the term “explanation” while others use the term “argument.” At times their definitions of these terms are very similar, while other researchers differentiate between the two. In our work, we chose to use the term “explanation” in order to be consistent with science standards (American Association for the Advancement of Science, 1993; National Research Council, 1996), which the teachers we work with need to address in their classroom practice. Our Definition of Scientific Explanation Like many science educators our framework for scientific explanation (Bell & Linn, 2000; Driver, et al., 2000; Jiménez-Aleixandre, Rodríguez, & Duschl, 2000; Sandoval, 2003; Zembal-Saul, et al., 2002), used an adapted version of Toulmin’s (1958) model of argumentation. Our explanation framework includes three components: a claim, evidence (similar to Toulmin’s data), and reasoning (a combination of Toulmin’s warrants and backing). The claim is an assertion or conclusion that answers the original question. The evidence is scientific data that supports the student’s claim. This data can come from an investigation that students complete or from another source, such as observations, reading material, archived data, or other sources of information. The data needs to be both appropriate and sufficient to support the claim. The reasoning is a justification that links the claim and evidence and shows why the data counts as evidence to support the claim by using the appropriate scientific principles. Consequently, we use a general explanation framework (claim, evidence, and reasoning) across different content areas in science. Educational researchers disagree about whether an explanation framework has to be domain specific or if the same framework can be used across all domains of science. Whether or not teaching general strategic knowledge proves useful for reasoning in context, is a complicated and unresolved issue (Perkins & Salomon, 1989). Passmore and Stewart argue that scientific inquiry is domain specific, which needs to be taken into consideration when designing curriculum (2002). Domain specific knowledge determines the types of questions asked, the methods used, and what counts as evidence (Passmore & Stewart, 2002; Sandoval, 2003). For example even in two areas of ecology, a scientist studying population dynamics may use mathematical models as evidence while a scientist studying field ecology may use frequency or counts of species. Although we agree that domain specific knowledge influences the inquiry practice, we conjecture that a general and useful explanation framework can be adapted across all domains of science. Argument is a form of thinking that transcends the particular content to which it refers (Kuhn, 1993). An explanation model, such as Toulmin’s, can be used to assess Scaffolding Scientific Explanations 5 the structure of an explanation, but it cannot determine the correctness of the explanation (Driver, Newton & Osborne, 2000). Scientific argument or explanation is a way of thinking that is not domain specific, but the general framework does need to be adapted to the specific content and context. Explanations in Classroom Practice Explanations are rarely a part of classroom practice (Kuhn, 1993; Newton, Driver & Osborne 1999). Furthermore, prior research on explanation in science classrooms has demonstrated some student difficulties in constructing and evaluating explanations. For example, students have difficulty using appropriate evidence (Sandoval & Reiser, 1997) and including the backing for why they chose the evidence (Bell & Linn, 2000) in their written explanations. During classroom discourse, discussions tend to be dominated by claims with little backing to support their claims (Jiménez-Aleixandre, Rodríguez & Duschl, 2000). Consequently, we focus on how to support students’ construction of scientific explanations in classrooms. Specifically, we examined the role of instructional and assessment scaffolds in supporting students’ written explanations. Scaffolding Student Learning First, we briefly discuss the history of scaffolding and why the research suggests that fading should be beneficial for greater student learning. Wood, Bruner and Ross (1976) originally introduced the term “scaffolding” in 1976. They introduced the term in the context of adult-child interactions where the more knowledgeable adult tutors the child to complete a task they would be unable to do on their own. With the help of scaffolds, learners can complete more advanced activities and engage in more advanced thinking and problem solving (Bransford et al., 2000). We define scaffolds as the supporting structures provided by people or tools to promote learning. Scaffolds can promote different types of knowledge like metacognitive expertise, inquiry abilities, and content knowledge. Although Wood et al. did not originally connect scaffolding to Vygotsky’s zone of proximal development, a number of educational researchers since then have explicitly made this connection (Hogan & Pressley, 1997; Palincsar & Brown, 1984). The zone of proximal development (ZPD) defines the area between a child’s independent problem solving capabilities and the level of potential problem solving capabilities with the guidance of people or tools (Vygotsky, 1978). Stone argues that scaffolds allow students to a