When knowledge is wrong…

Babies are born knowing physics. They express surprise when an object appears to be suspended in mid-air or pass through walls (nice article here). These are the primitive physics schemas we are all born with. Onto these, we add experiences from our lives: metals are cold; batteries run out of charge; the sun moves. Then in physics lessons we try to supplant this knowledge with formalised knowledge. With mixed results.


A metal cup to keep drinks cold.

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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.


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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Using Worked Examples to Reduce Cognitive Load in Physics

Screenshot from 2017-04-29 11-12-05

from Cognitive Load Theory – Sweller, Ayrea, Kalyuga 2011 (art by @@olivercavigliol – https://teachinghow2s.com/docs/CLT_chapter_summaries.pdf)

Learning how to solve problems is the key to becoming a physicist (here and here). The problem with problem solving is that you need to be pretty knowledgeable before you can make a good go at it. And we tend to teach new information and then put it into a problem in the same lesson. This doesn’t work for most learners.

The science of learning – cognitive load theory – has found the best way to to teach problem solving: worked examples.  Hattie puts the effect size of worked examples at 0.57 – 7 months extra progress per year.

Screenshot 2017-04-29 at 13.40.24

from Story of a Research Program by John Sweller

When a teacher models how to solve a problem, she is giving the guidance that novice physicists need. She will make the hidden process of solving the problem visible. It is a way in.

But then what? The jump from seeing someone do it to being able to do it yourself is still big.: “novice learners reach apoint of working memory overloadvery quickly” Hattie, Yates. 2014). Learners need a bridge.

One method is to give learners partially completed problems – this method is called problem completion. This reduces the cognitive load, allowing the learner to focus his working memory on fewer aspects of the problem.

Here is an example:

Worked Example

Terminal Velocity Q AQA 2016

AQA June 2016

Teacher’s explanation

Imagine you are standing at the board – ideally the question is projected adjacent to where you are explaining and making notes for the class:

  1. The weight of the ball is independent of the ball’s speed – it doesn’t change.
  2. The drag on the ball increases as the ball accelerates.
  3. The ball stops accelerating when the drag matches the weight – it has reached terminal velocity.

Completion Problems…

Going straight from worked example to whole questions is very challenging for most learners. Sentence starters reduce the cognitive load:

On 14 October 2012, Felix Baumgartner created a new world record when he jumped from a stationary balloon at a height of 39km. Above the Earth’s surface. 42s after jumping, her reached a terminal velocity of 373 m/s. Explain in terms of weight and drag how terminal velocity is reached.


  1. The weight ________________________________________________________________________
  2. The drag __________________________________________________________________________
  3. When the drag has increased _____________________________________________________

One completion problem will not be enough. You will need lots. There are plenty available in past papers, however, there is a cognitive advantage in including individuals in the class:

When his balloon experiment began to go wrong, Mr Rogers knew he had to jump. He was 5km high. Explain in terms of weight and drag why he reached terminal velocity as he fell.


  1. The weight ______________________________________________________________________
  2. The drag ________________________________________________________________________
  3. When the drag has increased ____________________________________________________.

Other insights from cognitative psychology include spacing out the practice and interleaving. I suggest revisiting these problems regularly and mixing them up with other questions. Aim for success – there are benefits for students getting it right. Optimum challenge is great, but getting answers wrong makes it more challening next time.

In my next blog, I will describe another strategy for reducing the cognitive load for novice physicists – cooperative learning.
I found @olivercavigiol teachinghow2s.com helpful in writing this blog.

Haven’t We Got Enough To Do Already? Why Science Teachers Should Teach Vocabulary and How to Make it Stick


There are words in the English language that science teachers wish the English department would teach – words like process, appropriate and monitor. We don’t expect anyone else to teach scientific vocabulary such as photosynthesis and nucleus, but if someone (English teachers?) could teach all of the rest, that would be great.

bitesize sankey

Tier 2 words: summarise, process, involved, x rather than y. http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/energy/heatrev5.shtml

Worse luck – it doesn’t work that way. If you want your students to be able to read science textbooks and understand exam questions, teaching this sophisticated, but non-specialist vocabulary is down to you.

Specialists call these words tier 2. Here is my strategy for teaching tier 2 words in science. Continue reading

Cooperative Reading

I started thinking about cooperative learning in 2010 and have made slow punctuated progress since. I know enough to write about it.

Back in 2010, I read and reread John Hattie’s Visible Learning. Among other strategies, I was drawn to cooperative learning.

Following a trail of references, I bought Graham Nuthall’s book: The Hidden Lives of Learners which confirms that students learn more from their peers than they do from their teachers.

Any teacher would be crazy not to make use of this. Continue reading

How Practical Work in Physics Supports Knowledge

Back in 1994, I began by PGCE at Oxford University. I was lucky to have a brilliant tutor, Brian Woolnough. He was an important academic: with Terry Allsop he wrote the key text Practical Work in Science. We respected him enormously.

The book was a review and analysis of science teacher’ practice – why we use practical work in science. My super-short summary is that we use practical work to:

  • develop practical skills and techniques;
  • be a problem-solving scientist;
  • get a ‘feel for phenomena’.

It was obvious that Brian was excellent in the classroom too. He was a showman and had an irreverant, maverick touch. In a full lecture hall, he solomnly picked up a copy of the National Curriculum and tossed it on the floor.

I also remember we caught him cheating demonstrating a physics practical that wasn’t working. He gave us a cheeky grin and said, “Well, it doesn’t matter if they learn it, does it?”

It is noticible that the summary list does not include “learn science knowledge” – practical work is pretty poor at helping learners master exam content. But it does support the learning of knowledge, by providing a concrete structure to build a schema around.

The more abstract and theoretical the concept, the more we need something concrete to attach the learning to. A practical activity provides a concrete experience that a skilled science teacher can build upon.

But it doesn’t happen automatically. The leap from concrete to abstract is generally too far for most learners to make solo. The gap needs to be bridged.

Recently, I have used Lemov’s Write/Rewrite to help my students link abstract concepts to concrete, practical work. I refer to the same practical experiences over and over again, spaced over weeks, to help my students make permanent memories, linking to abstract ideas. If the practical can’t be set up repeatedly, I bring in a key piece of equipment and photos to remind them and I set writing tasks (in a carefuly written sentence, explain….).

write rewrite chronometer


When I am confident that the have made a reliable connection between the abstract and concrete idea, I go about building on it. I ask them to make novel comparisons using a worksheet like the one below (see The Learning Scientists on Elaboration).


Elaboration (making inflexible knowlegde flexible)

As Brian said back in 1994 -“Well, it doesn’t matter if they learn it, does it?”