Benchmarks for Science Literacy: Chapter 15 THE RESEARCH BASE



Experimentation. Upper elementary- and middle-school students may not understand experimentation as a method of testing ideas, but rather as a method of trying things out or producing a desired outcome (Carey et al., 1989; Schauble et al., 1991; Solomon, 1992). With adequate instruction, it is possible to have middle-school students understand that experimentation is guided by particular ideas and questions and that experiments are tests of ideas (Carey et al., 1989; Solomon et al., 1992). Whether it is possible for younger students to achieve this understanding needs further investigation.

Students of all ages may overlook the need to hold all but one variable constant, although elementary students already understand the notion of fair comparisons, a precursor to the idea of "controlled experiments" (Wollman, 1977a, 1977b; Wollman & Lawson, 1977). Another example of defects in students' skills comes with the interpretation of experimental data. When engaged in experimentation, students have difficulty interpreting covariation and noncovariation evidence (Kuhn, Amsel, & O'Loughlin, 1988). For example, students tend to make a causal inference based on a single concurrence of antecedent and outcome or have difficulty understanding the distinction between a variable having no effect and a variable having an opposite effect. Furthermore, students tend to look for or accept evidence that is consistent with their prior beliefs and either distort or fail to generate evidence that is inconsistent with these beliefs. These deficiencies tend to mitigate over time and with experience (Schauble, 1990).

Theory (explanation) and evidence. Students of all ages find it difficult to distinguish between a theory and the evidence for it, or between description of evidence and interpretation of evidence (Allen, Statkiewitz, & Donovan, 1983; Kuhn 1991, 1992; Roseberry, Warren, & Conant, 1992). Some research suggests students can start understanding the distinction between theory and evidence after adequate instruction, as early as middle school (Roseberry et al., 1992).

Nature of knowledge. Students' ideas about the nature of knowledge and how knowledge is justified develop through stages in which knowledge is initially perceived in terms of "right/wrong," then as a matter of "mere opinion," and finally as "informed" and supported with reasons (Kitchener, 1983; Perry, 1970). This research provides some guidance for sequencing the benchmarks about the nature of scientific knowledge. For example, it suggests that students may not understand before they abandon their beliefs about knowledge being either "right" or "wrong" that scientists can legitimately hold different explanations for the same set of observations. However, this research does not say when, how quickly, and with what experiences students can move through these stages given adequate instruction. Several studies show that a large proportion of today's high-school students are still at the first stage of this development (Kitchener, 1983; Kitchener & King, 1981). Further research is needed to specify what school graduates could understand, if from a young age they were taught that different people will describe or explain events differently and that opinions must have reasons and can be challenged on rational grounds.
Research in the 1960s and 70s used multiple-choice questionnaires. Recent studies using clinical interviews reveal discrepancies between researchers' and students' understanding of the questions and the proposed answers in those questionnaires. This finding raises doubt about the earlier studies' findings because almost none of them used the clinical interview to corroborate the questionnaires. Therefore, the following remarks draw mainly upon the results of the relatively recent interview studies.