Ratio, Load and Difficulty – 3 Lesson Sliders

ratioloaddifficulty v3

In my mental lesson control booth, I have three sliders I try to get right.


The first slider is ratio. I learnt this idea from Teach Like a Champion by @Doug_Lemov, who got it from Dave Levin from Kipp.

Ratio is the amount individual students spend actively thinking in class compared to the total lesson time. For example, in a teacher-to-one Q+A session, the ratio is low for every child who isn’t asked the question – most children don’t think much in those circumstances. You can increase the ratio by asking a question to the class and then getting them to answer it in pairs.

I used to worry that increasing ratio meant that direct instruction and teacher- modelling were low ratio. But pushing the ratio slider up a little in these activities means the teacher says what she needs to say as clearly and succinctly as possible, before the learners get active. That’s a good thing.


By load, I mean cognitive load. I want to bring this as low as I can so that my students are thinking about the thing I want them to learn. I reduce all of the extraneous ‘noise’ – especially for novices.

This week I have been working on direct speech with my class. There are many loads on a novice with writing direct speech: paragraphs, capital letters, commas, question marks, inside the speech marks or out. Added to that, they wanted to write their own dialogue.

I pulled the load slider as low as I could – we used goal free to look at speech from a book. They wrote their dialogues as playscripts first before converting to direct speech. Each element was difficult, but I reduced the load.


When I first learnt about cognitive load, I thought it meant make the thinking easy. It doesn’t. Cognitive load theory simply says take out the extraneous thinking – the undesirable difficulties and make the thinking about the thing you want to achieve. And that thing can (and should) be difficult.

There is an optimum difficulty for tasks – Bjorn calls them desirable difficulties (see here). He makes a terribly important point – one that I missed for many years – performing well in class is not the same as learning well. The struggle is important.

So whenever you can:

  1. turn up the ratio
  2. turn down the load
  3. set the difficulty to desirable.


My experience with ‘goal-free’ – a Cognitive Load Theory strategy

@Olivercaviglioli ‘s wonderful document on Cognitive Load Theory here introduced me to the “Goal-Free Effect” – a Cognitive Load Theory (CLT) strategy that I was unfamiliar with. Goal-Free was the first CLT strategy – that’s what comes of learning your theories from blogs.

The strategy reduces cognitive load by removing the actual question from the problem, leaving just infromation, often in the form of a diagram.

This is how I’ve been using it to help my pupils prepare for the maths reasoning papers in the SATs.


Goal-Free KS2 Maths Reasoning Question

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The single most important thing for teachers to know… Version 2

WIliam CLT

Dear Reader,

Yesterday I published a post on Cognitive Load Theory (here) and how I use it in class. I was concerned that although I had been careful in my reading, I was sure to have “invented” modifications of my own (also known as “mistakes”). Sure enough, several readers kindly (and gently) pointed out where I had been creative/careless/wrong. My thanks especially to  ,  for his great essay here and @FurtherEdagogy.

This is version two of my post.

Please continue to comment – and never assume I am an expert.



Cognitive Load Theory, and How to Use It 2.0

Here is my explanation for how Cognitive Load Theory works and how to use it.

CLT schematic (3)

The elements of Cognitive Load Theory – long-term memory, working memory and external memory.

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The single most important thing for teachers to know…

WIliam CLT

Dear Reader,

There is a lot being written about Cognitive Load Theory (CLT) and how important it is. I have written this blog to share my understanding – please send me corrections, recommendations and advice.

My own understanding has been developed through:

  • Hattie’s ‘The Science of How We Learn”
  • Willingham’s “Why Students Hate School”
  • Kellog’s “The Psychology of Writing”
  • Oliver Caviglioli’s summary of Sweller’s “Cognitive Load Theory”

My aim it to add something useful for teachers. I am a teacher, not a psychologist. Please send me corrections and recommendations so that I can improve this post.

Thank you for taking the time to read it. I hope it is useful.


Cognitive Load Theory, and How to Use It

Here is my explanation for how cognitive load theory works and how to use it.

CLT schematic (2)

A Model Of Cognitive Load Theory

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Integrating Questions and Diagrams to Reduce Cognitive Load for Novice Physicists

I think this will be the last of my problem-solving blogs for a while – it’s a little one about reducing the split-attention-effect.

In this series of blogs, I have suggested strategies to reduce the cognitive load of problems, so that novices can focus attention on the elements you want. This one is about text and diagrams.


From AQA 2016

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Going Goal-Free to Learn How to Solve Physics Problems

In previous posts, I have been writing about teaching problem solving (here, here and here). This post describes a strategy that appears counter-intuitive, until you think about what you really want your students to learn.

AQA Phy Jun16

from AQA Jun 16 Physics A-Level Unit 2 Paper

When you use this question in class, which of the following learning goals is most important to you:

A: learning how to solve this type of problem

B: finding out how much vertical supporting force the rock really supplies.

I’m assuming that you don’t really care about the answer to the question.

When you set this question, any student who can’t solve it is actually less likely to solve it or a similar one next time (Hattie and Yates. 2011 – Visible Learning and the Science of How We Learn. p151). Your student is so caught up in the goal (solving the problem) that she has no working memory left to reflect on learning the strategy.

This blog describes the strategy that prompted John Sweller to develop Cognitive Load Theory (CLT) – the Goal-Free strategy (read more about its history here).

Reducing the cognitive load allows the learner to learn. In the question above, simply cut off the bottom line. You then have a situation to explore with your students – the boy on the plank.

I like to go cooperative at this stage, asking students to discuss the situation in turns. I use a strategy I learned from Jakob Werdelin, a cooperative learning specialist, called Word-Round. In groups of four, students have 20 seconds to talk about the situation in the question. After 20s, the next team member speaks. The teacher listens in to pick up any useful and interesting points to share with the class after the Word-Round is finished. (Another cooperative strategy that works well in this situation is Think-Pair-Share).

A considerable amount of learning has happened by this stage, especially if your learners recognise the situation as a familiar one involving beams with two supports. It is possible that your students are now ready to tackle the problem. You may wish to demonstrate the working yourself or you might prefer to give a partial solution and allow your students to complete it.

Going Goal-Free might sound directionless, but it is the fast route to problem solving.