A learning cycle consists of three phases: exploration; conceptual invention; and expansion of an idea. These phases parallel Piaget's functioning model of assimilation, disequilibrium and accommodation, and organization respectively. The learning cycle perceives students as actors rather than reactors to the environment. Inherent in that perception are three assumptions, that: (1) each of the three phases is necessary; (2) the sequence of phases must be exploration, conceptual invention, and expansion of the idea; and (3) that the form of the exploration is student investigation with materials. Reported are seven experiments conducted to ascertain the impact of each on students' achievement of conceptual understanding and attitudes toward the concept. Concepts and principal variable (assumption) tested included: motion (form); falling bodies (sequence); mass (necessity); measuring heat in solids (necessity); some properties of an electric circuit (necessity); electricity at rest (form); and currents and magnetism (form). Methodology, results, and conclusions are reported. In addition, data related to student attitudes about laboratory work are reported and discussed. Among the supporting documentation in appendices are materials related to each experiment. These include teacher's guide, student materials used with experimental and control groups, evaluation materials, and evaluation results. (JN)