in the new system of concepts (Gelman and Lucariello, 2002, discuss this as forming rerepresentations) (see also Lehrer et al., 2000).

Even preschool children can use many of these heuristic techniques in limited contexts and in domains they understand, although they certainly do not yet coordinate them in the service of serious model-based reasoning. For example, even 3-year-olds can engage in analogical reasoning (Goswami and Brown, 1990); they can also engage in inference to best explanation, as when they infer a hidden causal mechanism to explain an observable event (Bullock

BOX 4-1

An Example of Discovery Argumentation

An example of a powerful form of discovery argumentation is the “bridging analogies” strategy (Brown and Clement, 1989; Clement, 1993). In this strategy, one identifies a target situation in which students’ initial intuitions are at variance with the expert analysis. For example, students do not see a book resting on a table as involving balanced forces (i.e., the force of the book on the table is equal and opposite to the force of the table on the book). Instead, they think that only the book is pressing on the table, or that it is pressing down more than the table is pressing up (hence, the book stays down). In fact, they often don’t think of a table as the sort of thing that can exert a force; it is conceptualized as a passive resistance or support.

Then one looks for an anchoring intuition—a situation in which the students’ intuition is in line with the expert analysis, even though they may not yet share the same general conception of force with the expert. For example, students see a book resting on an outstretched hand as a clear case of balanced forces, because the student can actively feel and imagine exerting greater and greater force as more books are piled on to actively compensate for the weight of the book.

Students initially see these two situations as entirely different from each other. Then one presents a series of bridging analogies—new situations that are intermediate between the target and the anchor, such as a metal coiled spring. The metal coil shows visible compression when the book is placed on it, which helps the student see the situation as like the hand, with which the student can feel the push and counterpush. Yet unlike the hand, it is an inanimate object. Students can engage in cycles of reasoning about these situations and in the process construct a new model of the situation, in which they can imagine the molecules in the table undergoing compression when the book is placed on it and pushing back with equal and opposite force. They can they test their prediction by checking if, in fact, there is a (slight) compression of the table when the book is placed on it.

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