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External representations, including pictures, graphs, text, gestures, and utterances, are key components of all curricular materials in physics. Such representations play a key role in cognitive function, particularly insofar as individuals interpret the meanings of and apply meanings to these representations. We previously proposed a model of how individuals can make meaning of and with external representations through layered analogies and applied this model to learning abstract ideas in physics, i.e. EM waves. [1] [2] We extend this model in two ways. (1) We distinguish individuals’ interpretations of representations, which can be highly variable and fleeting, from the physics community’s agreed upon interpretations, which are more stable and coherent. (2) We describe these two dimensions of representation use: abstraction based on the community consensus of concepts and salience based on readily accessible pieces of knowledge for an individual. [ABSTRACT FROM AUTHOR]

In physics instruction we often begin by presenting students with an abstract principle, and then illustrating the principle with one or more examples. We hope that students will use the examples to refine their understanding of the principle and be able to transfer the principle to new situations. However, research in cognitive science has shown that students’ understanding of a new principle may become bound up with the example(s) used to illustrate it. We report on a study with physics students to see if this “specificity effect” was present in their reasoning. The data show that even students who understand and can implement a particular physics principle have a strong tendency to discard that principle when the transfer task appears superficially similar to their training example. [ABSTRACT FROM AUTHOR]