A child is not a little adult, nor a learner a little scientist. Children’s concepts differ in structure and meaning from those of adults. Both Vygotsky (children have different kinds of concepts from adults; they don’t have true concepts until puberty) and Piaget (there are shifts between major periods which can be interpreted as changes in representational formats and processes that operate on them) would argue that there are fundamental changes in mental machinery from childhood to adulthood. As such, how to learn or be taught in a domain is quite different from how to perform or ‘do’ in a domain (i.e., learning science vs. doing science). The epistemology of most sciences, for example, is often based upon experimentation and discovery and, since this is so, experimentation and discovery should be a part of any curriculum aimed at ‘producing’ future scientists. But this does not mean that experimentation and discovery should also be the basis for curriculum organization and learning environment designing. Modern curriculum developers and reformers who often refer to themselves as constructivists tend to confuse the epistemological basis of a domain (i.e., how knowledge is acquired and the accepted validation procedures of that knowledge in a domain) with the psychological and pedagogic bases for teaching in that domain (i.e., strategies of instruction or a style of instruction). In other words, they fail to distinguish between learning and doing and thus overlook the fact that students are not miniature experts practicing something, but rather that they are novices learning about something.

Evidence for the superiority of guided instruction is explained in the context of our knowledge of human cognitive architecture, expert–novice differences, and cognitive load. Although unguided or minimally guided instructional approaches are very popular and intuitively appealing, the point is made that these approaches ignore both the structures that constitute human cognitive architecture and evidence from empirical studies over the past half-century that consistently indicate that minimally guided instruction is less effective and less efficient than instructional approaches that place a strong emphasis on guidance of the student learning process. The advantage of guidance begins to recede only when learners have sufficiently high prior knowledge to provide “internal” guidance. Recent developments in instructional research and instructional designmodels that support guidance during instruction are briefly described.