The move from behaviorism to constructivism emphasized the importance of prior knowledge in learning. The child-as-scientist metaphor, as also the work of Ausubel [#!ausubel!#], led to the belief that just as scientists' conceptions are affected by pre-existing conceptions, students' learning is affected by their pre-conceptions. It was hence thought necessary to study prevailing conceptions among students.
Various topics such as force, curvilinear motion, torque, simple circuits, light, heat, life, mole concept, atomism, evolution etc. have been studied. It has been seen that notions not conforming to scientific understanding of concepts prevail despite formal instruction. They are referred to as alternative conceptions or alternative frameworks by education researchers. Pfundt and Duit [#!fundt!#] report more than 4000 studies in their bibliographic collection spanning about two decades of research.
Some of the research on conceptual structure and conceptual change has used a cognitive science methodology of expert-novice comparisons [#!kaufman!#]. In these studies, expertise is first determined in terms of performance followed by an analysis of cognitive processes that mediate performance. A model consisting of knowledge representation, strategies and mechanisms of learning is proposed, to account for the observed differences in performance. Learning sequences are then designed to enable attainment of superior performance. Several tools have been used for studies of conceptual structure, the most prominent being the concept map [#!novak-90!#] described in the next section.
Another important trend in the studies of conceptual structure is based on the assumption that students' alternative frameworks mirror the historical development of a concept. Such comparative studies are fewer than those of student's naive conceptions and are confined to developmental studies in a few subject areas, like evolution and mechanics. Several studies claim that students' conception of evolution are primarily Lamarckian [#!bishop!#] [#!jimenez!#] [#!settlage!#]. Many of these researchers have suggested and evaluated teaching strategies to affect conceptual change. It [#!jimenez!#] has been indicated that strategies that draw from historical materials increase students' understanding of evolution.
Saltiel and Viennot [#!saltiel!#], observe that students' reasoning in mechanics resembled those of Philoponus (6th century). Halloun and Hestenes [#!halloun!#] remark that Buridan's (14th century) notion of impetus is a clear articulation of student's vague ideas. In an article addressing the relevance of cross-cultural studies, Thijs and his colleague have included a concise overview of studies relating to concepts in physics and their historical parallels. [#!thijscul!#]