SOLO Taxonomy

The SOLO taxonomy, standing for the Structure of Observed Learning Outcomes, is a model for describing the increasing complexity of a student's understanding of a topic, developed by educational psychologists John Biggs and Kevin Collis and set out in their 1982 book Evaluating the Quality of Learning. It describes five levels through which a learner's response to a task typically progresses: prestructural, where the learner has no real grasp of the topic; unistructural, where they can handle one relevant aspect; multistructural, where they can handle several aspects but not yet connect them; relational, where they integrate those aspects into a coherent whole; and extended abstract, where they can generalize that understanding to new, untaught contexts. Unlike taxonomies that classify types of learning objective in advance, SOLO is applied after the fact to classify the structural complexity of what a student actually produced, and it is widely used by teachers to write assessment criteria and to plan questions that push students toward deeper levels of understanding.