SOLO Taxonomy – 5 Levels of Learning Complexity

Biggs SOLO Taxonomy definition and stages, explained below

The SOLO taxonomy stands for ‘structure of observed learning outcome’. It provides a framework for analyzing a student’s depth of knowledge.

It was developed by John Biggs as an alternative to Bloom’s taxonomy of knowledge.

The SOLO taxonomy is considered a more practical framework than Bloom’s due to its focus on observable outcomes rather than internal cognitive processes.

The SOLO taxonomy contains 5 levels of knowledge, from simple to complex:

  1. Prestructural
  2. Unstructural
  3. Multistructural
  4. Relational
  5. Extended Abstract

At the lower levels, students demonstrate lower-order cognitive skills, while at higher levels students demonstrate the ability to use complex inductive reasoning strategies.

Definition of the SOLO Taxonomy

The structure of observed learning outcomes taxonomy (SOLO taxonomy) is a tool for measuring how well a student understands a topic.

It describes 5 levels of understanding from simple to complex. It is widely used for designing curriculum outcomes and assessment tasks that get progressively more difficult as students move through their education.

5 Levels of the Taxonomy

The 5 levels of the taxonomy are:

  • Prestructural
  • Unistructural
  • Multisrtuctural
  • Relational
  • Extended Abstract

The first 3 levels represent quantitative thinking, which Biggs argues tends to involve deductive reasoning and surface analysis. The final 2 levels move into a qualitative approach that focuses on depth of knowledge and understanding on a topic.

Here are explanations of each level of learning:

1. Prestructural

At the prestructural stage, students don’t have any understanding of the topic. This may be because they’ve never encountered it before!

Biggs argues that “prestructural responses simply miss the point” and “show little evidence of relevant learning” (Biggs & Tang, 2007, p. 87).

We can observe that a student is in the prestructural stage when they respond to questions with simple answers like:

  • “I don’t know”
  • “I’m parroting what I am supposed to say”, or
  • With an irrelevant comment.


When I grade papers, I notice this all the time. A paragraph may be totally off topic, filled with factual inaccuracies, or totally copied from a source text. This shows me that the student completely misunderstands.

Be Aware

Biggs reminds us that sometimes a person will give a long and seemingly impressive response to a question, but it may still be at the prestructural stage.

He uses the example of a politician speaking a lot, but not actually answering the question they were asked.

2. Unistructural

A student with unistructural understanding tends to understand only one or two elements of the task, but not the whole.

At this level, a student may be able to identify and name a few things and follow simple procedures that they have been taught.

While some elements of a topic may be covered by the student, they will also miss many more important parts of the topic that are required to truly understand it.

A student who provides a unistructural response to a question would likely:

  • Be able to give a vague or general answer.
  • Know some terms relevant to the topic.
  • Not be able to explain the terms in depth when pushed.

A Quote

Biggs explains: “Unistructural responses deal with terminology, getting on track but little more” (Biggs & Tang, 2007, p. 87).

3. Multistructural

At the multistructural level, the student has begun to acquire a lot knowledge, but can’t put it together yet.

The student’s knowledge remains at the level of remembering, memorizing and parroting what they have learned. The student therefore has surface level understanding. They could not use a concept in new and innovative ways because they simply don’t understand it well enough.


The multistructural student is like the builder without his tools: all the pieces are there, but he doesn’t know how they connect. You may have felt this way when you unpacked some Ikea furniture and it’s been laid out upon your floor in bits!

4. Relational

The relational stage is the first that shows deep qualitative understanding of a topic and more complex thinking skills.

At the relational level, students start to see how the parts of a topic are put together. They can:

  • Identify patterns.
  • Explain how parts of a topic link together.
  • Compare and contrast different elements of a topic.
  • View a topic from several perspectives.

Central to relational knowledge is the ability to create structures and systems for sorting knowledge. Students begin to explain connections between things by using systemic and some theoretical modelling.

A Quote

As Biggs argues: “a qualitative change in learning and understanding has occurred. It is no longer a matter of listing facts and details” (Biggs & Tang, 2007, p. 87).

5. Extended Abstract

At the extended abstract stage, students have a sophisticated understanding of the topic and can apply it in various contexts.

Biggs argues that the essence of the extended abstract response “is that it goes beyond what has been given” (Biggs & Tang, 2007, p. 87). In other words, students can create new knowledge and apply the knowledge they have in multiple contexts due to their deep understanding of the topic.

An Example

For example, a student may laern something in the classroom and be able to apply it in their lives outsive the classroom in an entirely different context.

Students may also be able to generate theoretical ideas and then use them to make assumptions about future events.

Bigg's solo taxonomy explained

SOLO Taxonomy vs Bloom’s Taxonomy

Biggs’s taxonomy is well respected as an alternative to Bloom’s taxonomy for assessing student behavioral and learning objectives.

While Bloom’s taxonomy describes many unobservable cognitive skills, the SOLO approach focuses on observable evidence of a student’s understanding. This makes it very useful for the assessment of a student’s understanding of topics.

In Bloom’s taxonomy, you may come across many unobservable and unassessable verbs to describe knowledge and understanding. Some examples are below:

blooms taxonomy, explained below

By contrast, the SOLO taxonomy focuses on outcomes of knowledge rather than descriptions of knowledge itself. The taxonomy provides vocabulary that clearly conveys what students should be able to demonstrate by the end of a course.

This means that Biggs’s approach is very useful for writing assessment learning outcomes. Below is a collection of observable verbs that the SOLO approach recommends.

SOLO Verbs (How to use the Framework in Curriculum Design)

Biggs designed the SOLO model for curriculum design in higher education. It is a part of his broader concept of constructive alignment.

Constructive alignment involves ensuring that the things we teach in our lessons:

  • Are in tune with our assessment content.
  • Prepare students for the things we assess our students on.
  • Are at an appropriate ability level in relation to the summative assessment.
  • Are cognitively challenging.
  • Use constructivist teaching strategies.

The SOLO framework, as a practical component of constructive alignment, helps us:

  • Create learning outcomes.
  • Assess students’ depth of knowledge.

As Biggs argues, this taxonomy “can be used to define course intended learning outcomes, which describe where students should be operating, and for evaluating learning outcomes so that we can know at what level individual students actually are operating.” (Biggs & Tang, 2007, p. 87)

To help guide you, you may like to use verbs that relate to each level of understanding. These verbs will guide you as you attempt to create learning outcomes that are at the appropriate difficulty level.

Advantages and Disadvantages of Bigg’s Model


Advantages of the SOLO taxonomy include:

  • Educators can use the verbs from the taxonomy to create learning outcomes. Unlike Bloom’s taxonomy, the verbs in the SOLO taxonomy are all observable, making them ideal for assessments.
  • It provides a framework for creating progressive curricula that gradually increase in difficulty level.
  • It provides a framework for thinking about what you want your students to know and at what stage.
  • It helps you think through what grade you will give a student by explicitly outlining how to identify depth of understanding.


Disadvantages include:

  • The model doesn’t take into account difficulty of topics themselves. Some topics (such as brain surgery!) require extreme difficulty to reach levels 3 or 4 of the taxonomy. Other topics may be easy to understand, manipulate and theorise at level 5 of the taxonomy (extended abstract level). So, even very difficult postgraduate level curricula may require lower-order verbs within their learning outcomes.
  • The model assumes courses should contain learning outcomes and places high value on assessment. Some educators may believe that assessment and learning outcomes stifle creativity and student-led learning and are therefore inappropriate.

Final Thoughts

The structure of observed learning outcomes (SOLO) taxonomy is a very useful framework for thinking about how well a student should, or does, understand a topic. I find it very beneficial for both writing curricula and assessing students’ work.

I reflect on it regularly when considering what grade I should give a student as it gives me a framework for considering how deep their understanding truly is.


Biggs, J.B., and Collis, K.F. (1982). Evaluating the Quality of Learning. New York: Academic Press.

Biggs, J. (1999). Teaching for Quality Learning at University. SHRE and Open University Press.

Biggs, J., & Tang, C. (2007). Teaching for quality learning at university. What the student does (3rd Ed.). Berkshire: Society for Research into Higher Education & Open University Press.

Brabrand, C., & Dahl, B. (2009). Using the SOLO model to analyze competence progression of university science curricula. Higher Education, 58(4), 531-549.

Website | + posts

Dr. Chris Drew is the founder of the Helpful Professor. He holds a PhD in education and has published over 20 articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education. [Image Descriptor: Photo of Chris]

2 thoughts on “SOLO Taxonomy – 5 Levels of Learning Complexity”

Leave a Comment

Your email address will not be published. Required fields are marked *