Learning involves the integration of new information into existing knowledge. Generoting explanations to oneself (self-explaining) facilitates that integration process. Previously, self-explanation has been shown to improve the acquisition of problem-solving skills when studying worked-out examples. This study extends that finding, showing that self-explanation can also be facilitative when it is explicitly promoted, in the context of learning declarative knowledge from an expository text. Without any extensive training, 14 eighth-grade students were merely asked to self-explain after reading each line of a possage on the human circulatory system. Ten students in the control group read the same text twice, but were not prompted to self-explain. All of the students were tested for their circulatory system knowledge before and after reading the text. The prompted group had a greater gain from the pretest to the posttest. Moreover, prompted students who generated o large number of self-explanations (the high explainers) learned with greater understanding than low explainers. Understanding was assessed by answering very complex questions and inducing the function of a component when it was only implicitly stated. Understanding was further captured by a mental model onolysis of the self-explanation protocols. High explainers all achieved the correct mental model of the circulatory system, whereas many of the unprompted students as well as the low explainers did not. Three processing characteristics of self-explaining are considered as reasons for the gains in deeper understanding.

For the past two decades, a growing amount of research has shown that the use of analogies in science teaching and learning promotes meaningful understanding of complex scientific concepts This article presents a study in which multiple analogies were used as scaffolding to link students' prior understanding of daily life events to knowledge of the scientific domain. The study was designed to investigate how multiple analogies influence student learning of a complex scientific concept: the electric circuit. We used several analogies in a set of learning materials to present the concepts of parallel and series circuits. Thirty-two fourth graders participated in this study and were randomly assigned to four groups. The four groups were named nonanalogy (control), single analogy, similar analogies, and complementary analogies, according to the materials they used in this study. The results demonstrated that using analogies not only promoted profound understanding of complex scientific concepts (such as electricity), but it also helped students overcome their misconceptions of these concepts. In particular, we found that the reason the students had difficulty understanding the concept of electricity was because of their ontological presupposition of the concept. Implications for teaching and learning are discussed. ß 2005 Wiley Periodicals, Inc. J Res Sci Teach 42: 2005 We always try to use old memories to recollect how we solved problems in the past. But nothing's ever twice the same, so recollections rarely match. Then we must force our memories to fit-so we can see those different things as similar. To do this, we can either modify a memory or change how we represent the present scene . . . . How hard it will be to make such a match depends both on which agents are now active in your mind and on the levels of their priorities-in short, on the context already established. -Marvin Minsky (1985, 1986.

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