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Introduction to the SOLO taxonomy

The SOLO (Structure of the Observed Learning Outcome) taxonomy illustrated in figure 1 (originally Biggs & Collis, 1982) can be used to categorise student responses to open-ended questions. The rubric used to assess your ePortfolio is based on the SOLO taxonomy.

SOLO illustrates the qualitative differences between student responses as it describes levels of understanding. It classifies outcomes in terms of their complexity, so that a judgement may be made on the quality of student responses to assessment tasks.

The SOLO taxonomy classifies understanding into five (5) levels:

  1. Prestructural: at this level the learner is missing the point
  2. Unistructural: a response based on a single point.
  3. Multistructural: a response with multiple unrelated points.
  4. Relational: points presented in a logically related answer.
  5. Extended abstract: demonstrating an abstract and deep understanding through unexpected extension.

SOLO Taxonomy The Structure of the Observed Learning Outcome (SOLO) taxonomy (Adapted from Biggs & Tang, 2011)

Biggs (n.d.) provides the following explanation of how we understand and learn, “At first we pick up only one or few aspects of the task (unistructural), then several aspects but they are unrelated (multistructural), then we learn how to integrate them into a whole (relational), and finally, we are able to generalise that whole to as yet, untaught applications (extended abstract)”.

Optional activity:

To review the SOLO taxonomy you can view three minutes of the video Understanding, from Teaching Teaching & Understanding Understanding, section 3 (3:15 - 6:18).


Biggs, J. B., & Tang, C. (2011). Teaching for quality learning at university (4th ed.). Berkshire: Open University Press.

Biggs, J. (n.d.). SOLO taxonomy

Biggs, J. B., & Collis, K.F. (1982). Evaluating the quality of learning. The SOLO taxonomy (Structure of the Observed Learning Outcome). New York: Academic Press.

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This article is from the free online course:

Introduction to Learning and Teaching in Higher Education

UNSW Sydney