Chi (1992; Chi and Slotu, 1993; Slotta, Chi and Joram, 1995) suggests that students experience difficulty in learning certain physics concepts because they inappropriately attribute these concepts with the ontology of material substances(MS). According to accepted physics theory, these concepts (e.g., light, heat, electric current) are actually a special type of process that Chi (1992) calls "Constraint-Based Interactions" (CBI). Students cannot understand the process-like nature of these concepts because of their bias towards substance-like conceptions, and also because they are unfamiliar with the CBI ontology. Thus, conceptual change can be facilitated by providing students with some knowledge of the CBI ontology before they receive the relevant physics instruction. This CBI training was provided by means of a computer-based instructional module in which students manipulated simulations as they read an accompanying text concerning four attributes of the CBI ontology. A control group simply read a (topically similar) text from the computer screen. The two groups then studied a physics textbook concerning concepts of electricity, and performed a post-test which was assessed for evidence of conceptual change. As a result of their training in the CBI ontology, the experimental group showed significant evidence of conceptual change with regards to the CBI concept of electric current.