More specifically, sciences employ an iconic sign system (De Westelinck et al., 2005) and have visualisations (Kali * Linn, 2008) and argumentation deeply rooted into the study material. In science classes, these visual representations enable scientific meanings to be constructed and make meanings that no teacher or student can readily convey in a different mode of communication or in one mode alone. These visualisations would affect the shaping of knowledge in a positive way (Kress et al., 2010). Especially science teachers should therefore use graphic organizers in presentations during which they display the explicit structure of the information covered by previous classes.
In previous research (Casteleyn et al., 2012) we experimentally examined the impact of graphic organizers in an e-lecture during a social science course at university. Two versions of the e-lecture were created, both were in line with the principles of CTML, but one version used non-linguistic representations to organize the information. Results showed that there was no significant difference in knowledge acquisition, cognitive load and self-efficacy, but the participants preferred the version with graphic organizers. Johnson * Christensen (2011) retrieved a similar result when they compared simplified, visually rich slides to more traditional presentation styles. No differences in learning outcomes could be detected, but students appreciated the simplified, visually rich slides to a higher extent. With this paper we want to study the impact of graphic organizers on learning outcomes and mediating variables (self-efficacy (e.g. Chularut * DeBacker, 2004), cognitive load and appreciation of the learning material) in the context of a science class in secondary education.