The general aim of the contributions to this special issue was to foster learning in computer supported collaborative learning environments by designing instructional interventions that enhance collaboration between learners. Scripts and external representations were used as instructional interventions to support social and cognitive processes, respectively, during collaborative learning. ... [Show full abstract] Although, the interventions enhanced these social and cognitive processes, beneficial effects on learning outcomes were not always found. This discussion uses cognitive load theory, particularly the expertise reversal effect, to explain these results. It is concluded that the principles from this theory which pertains to individual learning, show great promise for the design of collaborative learning environments.