knowledge base as adequate. This implies that misconceptions will be long-lasting and difficult to eradicate. If it is backward, then the misconceptions may simply be a means to an end. In this case, these incorrect ideas might best be viewed as transient hypotheses which are later either refuted or modified in the light of experience to form the kernel of a more adequate explanation. With intermediates, the reason for errors does not lie with serious misconceptions as much as with an excessive use of irrelevant information. Once again, the fundamental issue may lie in how this information is being used. The use of forward reasoning may indicate a dogmatic reliance on existing knowledge. Backward reasoning may indicate that the subject is attempting to learn how to separate out the relevant from the irrelevant.
These implications suggest that an instructional emphasis on the importance of correct problem solving and the harmfulness of misconceptions may not be productive. The important part of learning may consist in testing and pondering the adequacy of one's explanations rather than achieving accurately implemented solution procedures. If this is so, then a greater instructional emphasis on explanation rather than problem solving might prove profitable. The "problembased learning" we mentioned at the beginning of this paper might at least be supplemented by "explanation-based learning."
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