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.
Research study
2.1. Research hypotheses Rooted in the theoretical framework described above we formulate two research hypotheses:
• compared to the condition without graphic organizers (NGOC), the condition with graphic organizers (GOC) will score significantly better regarding knowledge acquisition;
• compared to the condition without graphic organizers (NGOC), the condition with graphic organizers (GOC) will score significantly better regarding motivational variables (attitude toward behaviour, perceived usefulness, and intrinsic motivation) and will yield significantly lower scores regarding cognitive load.