This is part of a series of blogs detailing a discussion that I had with John Sweller in mid 2017. See all parts of this series on this page. 

Update: I have now written a book that summarises Cognitive Load Theory in concise and practical terms. John Sweller played a key role in the writing process and has described it as ‘An indispensable guide to Cognitive Load Theory for Teachers'. Find out more here. 

OL: These questions come from Raj who I met a few weeks ago. He lives up in Queensland. He’s just finished reading your book. I think it was that one (pointing to: Sweller J;Ayres PL;Kalyuga S, 2011, Cognitive load theory, 1st, Springer, New York)

JS: Yeah, okay, my sympathies to him

(both laugh)

OL: Yeah he’s a diligent guy. He used to be an engineer he’s just moved into education now.

(First question omitted due to overlap with previous content)

So the second question is: ‘Measuring cognitive load has been done by self-report, secondary tasks and physiological markers. What are the weaknesses of these as measures for cognitive load? And which measure (or combination of measures) is the most valid and reliable?’

JS: Ok. I routinely use self-report and I use self-report because it’s sensitive. That’s the first thing you need. You need something that’s reasonably sensitive to what the cognitive load is. You can have something that can measure cognitive load but you might need vast differences in cognitive load to use these tools. A cognitive load measure that only is sensitive enough to distinguish between someone who is almost asleep as opposed to someone who is concentrating is not much use.

OL: What questions do you ask?

JS: I use the Paas 1992 test which is ‘How difficult did you find this instruction?’ Paas uses his original version which is something closer to, ‘How much mental effort did you put into studying this material?’ They’re very heavily correlated. It’s quick, takes literally a few seconds, very sensitive.  You can easily get differences between conditions using that test. The other one that’s sensitive is secondary tasks. They’re just as good as using self-report but they’re messy to set-up. You’ve got to set-up some sort of system to allow the secondary task and sometimes the system that you set-up might involve apparatus and technology which in a normal classroom is pretty difficult to put in. The last one, physiological markers, have had endless work on them. They don’t work yet.  We don’t have physiological markers which are sensitive. We’ve got physiological markers which will demonstrate the difference between really studying something hard as opposed to staring out the window. That’s no use to us. We need something that really distinguished between, say, studying worked examples vs. solving a problem or studying a worked example in a split attention format as opposed to an integrated format. Paas’ question and secondary tasks will do this. The physiological markers, despite endless efforts by a lot of people around the world for years and years and years, don’t really work.

OL: Yeah, that makes sense. Ok, Following on from 2, ‘Which CLT effects do you have the most/least confidence in given the evidence base?’

JS: Oh, that’s unanswerable in a way. I mean, the ones that I list in the book, I’m confident in them. And I’m confident in them because my students and I have carried out several experiments which have demonstrated them. People around the world have carried out experiments. If you want a popularity contest then the one that people have most commonly been studying is worked examples. People all over have tested and done that. But split-attention is important, redundancy is important, the transient information effect, which is a very new one, that’s important. So ultimately my confidence is based on whatever data is available and I sort of have this vague subjective opinion as to which effects have been more studied than other effects. And if something has been studied a lot.

OL: It’s probably more robust.

JS: Yeah exactly.

Next post:

8. Can we teach collaboration?

All posts in this series:

  1. Worked Examples – What's the role of students recording their thinking?
  2. Can we teach problem solving?
  3. What's the difference between the goal-free effect and minimally guided instruction?
  4. Biologically primary and biologically secondary knowledge
  5. Motivation, what's CLT got to do with it?
  6. Productive Failure – Kapur (What does Sweller think about it?)
  7. How do we measure cognitive load?
  8. Can we teach collaboration?
  9. CLT – misconceptions and future directions

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