The Balance-Scale Dilemma: Either the Subject or the Experimenter Muddles Through

We examined two critiques of rule-assessment methodology: (a) the method does not take into consideration other rules that subjects use to solve problems, and (b) its multiple-choice format misrepresents subjects' cognitive level. In Study 1, high school students completed a paper-and-pencil, multiple-choice balance scale questionnaire. Their performance was assessed with Siegler's original rules and a revised set of rules that included an addition and a qualitative proportionality rule. Results showed that Siegler's Rule 3 was not homogeneous and that distinguishing specific patterns of answers among Rule 3 subjects increased the diagnostic value of the rule-assessment methodology. In Study 2, we compared rule-assessment methodology to the Piagetian clinical model. High school students solved balance-scale problems within each method. Results indicated an overall match between Piagetian levels and Siegler's rules, with the exception of Rule 3, suggesting again the pertinence of specifying alternative rules.     

Calibration: A Conceptual Framework Applied to Scientific Practices Which Investigate Natural Phenomena by Means of Standardized Instruments

This paper deals with calibration in scientific practices which investigate relatively well-understood natural phenomena by means of already standardized instrumental devices. Calibration is a crucial topic, since it conditions the reliability of instrumental procedures in science. Yet although important, calibration is a relatively neglected topic. We think more attention should be devoted to calibration. The paper attempts to take a step in this direction. The aims are two-fold: (1) to characterize calibration in a relatively simple kind of scientific practices; (2) to provide conceptual and taxonomic tools of broader scope that help to get a better understanding of calibration in more complex cases and other kinds of scientific practices. For this purpose, we first provide indications for why a conceptual framework is needed. Second, a bibliographic survey of works dealing with calibration is attempted. Third, we introduce different tools to enable a better understanding of calibration. Fourth, we turn to the elaboration of what we call a “simple exemplar” of calibration, illustrated through the case of the calibration of an equal-arm balance. Fifth, the tools previously introduced, and the framework of the simple exemplar, are applied to a more complex case of calibration: calibration procedures in X-ray experiments. This serves to show the work accomplished by the simple exemplar and to emphasize features of more complex cases of calibration. Eventually, we revisit and specify the nature, status, scope and value of the proposed framework.