1 Just-in-time, schematic supportive information presentation Abstract Cognitive load theory states that well-designed learning material minimizes extraneous cognitive load and optimizes germane cognitive load within the thresholds of available cognitive resources.In this study, the extraneous cognitive load is minimized by avoiding temporal split attention with regard to supportive information (i.e., conceptual models or 'theory') and the germane cognitive load is optimized by using schematic representations of this information to direct learner's attention to concepts relevant for learning. A 2x2 between-groups design with the factors supportive information (before or during practice) and schematic representation (before or during practice) was used to investigate whether this balance between extraneous and germane load leads to more effective and efficient learning. It was found that the 'supportive during, schema before' format indeed yielded a higher learning efficiency than the 'supportive before, schema before' and the supportive during, schema during' format but no differences were found for learning effectiveness (i.e., test performance). problem-based learning, and competency-based learning usually focus on (realistic and authentic) whole tasks or meaningful problems (Merrill, 2002;Reigeluth, 1999;. Such tasks and problems help learners master the necessary cognitive skills and transfer what is learned in school to their daily life or work settings.A potential pitfall of using such tasks is that, because of their complexity, they demand too much of the learner's cognitive system. Working memory capacity is limited and exceeding this capacity hampers learning (Baddeley, 1992;Miller, 1956;Sweller, 1988). The load imposed on working memory can be influenced in several ways. First, working on realistic tasks can be supported by sequencing tasks during practice from simple to complex (Reigeluth, 1983;1999) or by using low-load task formats, such as worked-out examples Van Gerven, Paas, van Merriënboer, & Schmidt, 2002) or completion tasks (van Merriënboer, Schuurman, de Croock, & Paas, 2002;van Merriënboer & de Croock, 1992). Second, information necessary to carry out the tasks can be presented just-in-time; in other words, precisely when the learner needs it for practice (van Merriënboer, Kirschner, & Kester, 2003; Kester, Kirschner, & van Merriënboer, in press). These instructional interventions aim at optimally utilize working memory capacity to facilitate cognitive skill acquisition. The latter approach is the focus of the current study. Cognitive LoadThe cognitive load that a learner experiences during learning and practice is caused by a combination of the complexity of the problem to be solved and the design of the instructional materials. Solving the problem yields intrinsic cognitive load which is determined by the number of elements in the instructional material (e.g., practice problems, subject-relevant information) and the degree of element interactivity. Low element interactivity is associate...