Effectiveness and use of optional scaffolds: an intervention study in biology lessons on phylogenetic trees

In heterogeneous classes, students require different levels of support to effectively learn complex content such as interpreting phylogenetic trees. Incremental scaffolds are a promising approach that considers students’ knowledge and skills and offers individual ways of working on tasks. These scaffolds consist of an initial prompt followed by a worked-out example. Current research on the effectiveness of incremental scaffolds for cognitive (knowledge) and motivational (self-efficacy expectations, intrinsic motivation) outcomes is inconsistent. This study explored the effects of incremental scaffolds (treatment 1) and their key components, prompts (treatment 2) and worked-out examples (treatment 3), when offered as voluntary, optional support. The comparison of the three treatments (N = 108 upper secondary school students; grade 11 and 12) showed no significant differences regarding students’ cognitive and motivational outcomes. Subsequent analyses revealed that optional support was mainly used by students with lower pre-knowledge, lower self-efficacy expectations, and lower intrinsic motivation. Simultaneously, students who used support scored lower on post-knowledge assessments and on a specific indicator of intrinsic motivation (interest/enjoyment). Our findings suggest that students who need support are the ones who use it. However, using support alone does not appear sufficient to compensate for differences compared to students who do not require support.