To PBL or NOT TO PBL (Is that the correct Question?)

I recently read an article produced by the NSW Centre for Education Statistics & Evaluation titled Cognitive load theory: Research that teachers really need to understand. It was a well written and easy to comprehend review of academic literature on Cognitive Load Theory. However, the article poses this proposed debate of how people learn best and broadly divides it into two approaches to teaching practice, explicit instruction vs inquiry learning. Last year I attended a PBL conference in Zurich and the same notion occurred in a debate between Professor Henk G. Schmidt, a pioneer of PBL versus Professor John Sweller.

Henk ‘McGregor’ Schmidt versus John ‘Mayweather’ Sweller

This debate was the educational equivalence of the recent Mayweather versus McGregor boxing match. In one corner, we have the inquiry or PBL approach, which many people believe  is about allowing students to discover or construct some or all of the information themselves. In the other corner, are those who believe that learners do best when they are provided with explicit instructional guidance in which teachers clearly show students what to do and how to do it.

However, I propose that these two approaches are not in opposition and a deep understanding of both approaches are needed by all teachers.

Cognitive Load Theory is about how students learn best

Cognitive Load Theory, as the title of the article suggests is definitely something that all teachers need to understand. In 1956, cognitive psychologist George Miller produced an influential paper title ‘The Magical Number Seven, Plus or Minus Two‘, which proposed that short-term memory is subject to certain limits including span and the quantity of information that can be stored at a given time. Cognitive load theory supports explicit models of instruction, because such models tend to accord with how human brains learn most effectively (Kirschner, Sweller & Clark 2006). Explicit instruction involves teachers clearly showing students what to do and how to do it, rather than having students discover or construct information for themselves. Furthermore, it is important that teachers understand the limitations of working memory and avoid making simple mistakes in instruction that produce cognitive overload and are harmful to student learning.

However, these mistakes can occur in teacher-centred instructional environments that focus on explicit instruction. Some examples include the ‘redundancy effect‘, which can occur when a teacher reads the text projected on a screen to students. This requires learners to process redundant information and inhibits learning because it overloads working memory. Another example is the ‘split attention effect‘, which occurs when learners are required to process two or more sources of information simultaneously in order to understand the material. An example, is when a diagram is used to explain a concept, but it cannot be understood without referring to a separate piece of explanatory text (common in worksheets). In this instance the learner is required to hold both sources of information in their working memory at the same time and to mentally integrate the two. This places a high cognitive load on the working memory, reducing the ability of the learner to transfer the relevant information to their long-term memory.

On the contrary, these issues also occur in student-centred instructional environments that focus on PBL. The most common issue is the creation of extraneous cognitive load, which is the ‘bad’ type of cognitive load, because it does not directly contribute to learning. For example, a common misunderstanding of PBL is ‘minimal guidance’. Therefore, teachers incorrectly see themselves as ‘guides on side’, rather than activators of knowledge. Facilitating an environment where students have to solve problems for themselves, with minimal guidance from the teacher is detrimental to student learning. This approach imposes a high cognitive load, but does little to encourage students to make meaning of information being learnt, often because the student’s attention is focused on solving the problem rather than the learning.

What is the intersection between PBL and Cognitive Load Theory?

It is important to note that cognitive load theorists do not advocate using all aspects of explicit instruction all the time. Indeed, they recognise the need for learners to be given the opportunity to work in groups and solve problems independently – but assert this should be used as a means for practicing newly learnt content and skills, not to discover information themselves (Clark, Kirschner & Sweller 2012, p. 6).

These approaches are aimed at promoting learner independence while managing cognitive load appropriately, depending on the learner’s novice/expert status … If the instructor provides some guiding principles, prior information, signposts along the way, and scaffolds and assistance where needed, there is less burden on working memory. (Martin 2016, p. 39)

So how can PBL benefit from an understanding of cognitive load theory?

Dr Michael McDowell the author of Rigorous PBL by Design provides some coherence to the alignment between PBL and Cognitive Load Theory. In his blog titled The Missing Ingredient in PBL: Direct Instruction he proposes that direct instruction is a missing approach in many problem and project based learning environments and as a result a significant number of students are not realizing the learning gains we [should] expect. Furthermore, he argues that we need to utilize effective direct instruction in the PBL/PrBL classroom specifically in situations where a ‘high intrinsic cognitive load‘ is placed on student memory as they are novice learners building new knowledge and skills.

John Hattie summarises explicit instruction as an approach in which:

The teacher decides the learning intentions and success criteria, makes them transparent to the students, demonstrates them by modelling, evaluates if they understand what they have been told by checking for understanding, and retelling them what they have been told by tying it all together with closure. (Hattie 2009, p. 206)

Great idea. How does this work in a classroom?

I recently visited a teacher in a year 5 classroom who attended a workshop presented by Dr McDowell. The teacher was utilising Project Based Learning as the primary pedagogy and students were working in groups to solve real world problems regarding the geography of Western Sydney. Existing within the classroom were the key elements of project based learning including entry event, driving and need to know list.

However, this approach was more than just minimal guidance, allowing students to construct their own knowledge.

The project wall showing the key elements of Project Based Learning

Firstly, there were clear benchmarks linking targeted instruction opportunities for students (often as a result of formative student assessment data). These benchmarks not only scaffolded the learning in project, but they also provided a clear need for explicit instruction. Both the ‘simple-to-complex’ and ‘part-whole’ approaches where utilised in the early benchmarks to afford students the opportunity to build their mental representations of knowledge in this project. The teacher was the key activator of this knowledge and explicit instruction was the driver.

Subsequent benchmarks, required students to make connections between the knowledge they had acquired, encoded and stored, and the project they were working on as a group. If the explicit instruction had not occurred, the result would be ‘extraneous’ cognitive load being placed on students as they attempt to solve the problem and work as a group.

Secondly, all learning intentions identified were represented as a transparent success criteria, showing the development of knowledge at a surface, deep and transfer level. Furthermore, within the success criteria there were clear models helping students reduce the burden on working memory and allowing them the opportunity to transfer the information into their long-term memory.


Clear success criteria and examples for students at surface, deep and transfer.
The integration of benchmarks with explicit success criteria at different levels within the project.


There is still considerable work to be undertaken in this area. However, hopefully this blog provides some coherence in the comparisons between PBL and Cognitive Load Theory, rather than the contrasting view that is often presented.




One thought on “To PBL or NOT TO PBL (Is that the correct Question?)

  1. Really comprehensive articleGavin discussing the debate between explicit (direct) instruction versus constructivist (inquiry based ) pedagogy I enjoyed reading your argument in which you demonstrate that the two approaches need not be mutually exclusive and that the best PBL practitioners ensure that there is intellectual rigour


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