👋 Hello {{first name | DistillED reader!}}
In this edition of ⚗️DistillED, we’re going back to what dual coding actually means and unpacking five common ways the idea mutates when it reaches the classroom.
In this edition
📊 Do Now: Quick Poll!
When you dual code a resource, what do you usually add?
What is Dual Coding?
Dual coding is what happens when an idea is encoded in a student's long-term memory in two forms: as language, and as an image. Each carries something the other doesn't, and a link between them means recalling one can bring back the other.
Allan Paivio spent forty years on this (Paivio, 2007). The part that matters for teaching is the link. A slide can make that connection possible, but putting a diagram beside a paragraph doesn’t guarantee students will connect the dots. One powerful way to strengthen the connection is to ask students to turn the diagram into words, or the words into a diagram.
Somewhere between the research and the classroom, dual coding stopped meaning a theory of how memory stores information and started meaning a way of designing resources. That kind of drift is known as a lethal mutation: when a practice begins with a solid evidence base but, somewhere in implementation, changes in a way that undermines its intended effect.
In typical DistillED fashion, here's what dual coding is — and what it isn't:
👎 Dual Coding IS NOT (Five Lethal Mutations):
The Decoration: A stock photo beside the text gives students nothing to connect it to. Decorative images perform worse than no image at all (Sundararajan & Adesope, 2020).
The Read-Along: Text on screen while we say the same words is one code delivered twice, and the duplicate gets in the way (Kalyuga, Chandler & Sweller, 1999).
The Vanishing Visual: If the diagram leaves the screen while the explanation continues, the two never meet in working memory.
The Copy: Reproducing a visual from the board is a motor task. The student produces nothing they weren't already given.
The Beautiful Organiser: A well-designed resource that gets received rather than used to think with. The design is right and the task is missing.
👍 Dual Coding IS:
A Picture That Adds Something: If the image only repeats the text, there's nothing to connect. It has to carry information of its own. A cross-section showing where the layers sit beats a photo of a volcano next to a paragraph about volcanoes.
A Task, Not Just a Resource: The visual is the prompt. What we ask students to do with it is where the learning happens, and we can't do that part for them. Same timeline on the board, but thirty seconds explaining it to a partner instead of thirty seconds copying it.
Either Direction Works: Words into a picture, or a picture into words. One is enough. Sketch what this paragraph described, or tell me what this diagram shows. Teaching supplies the first direction constantly and rarely asks for the second.
👉 Read The Simple Model of the Mind for how the two systems sit inside working memory.
Dual Coding with Mini-Whiteboards
Take a look at The Mini-Whiteboard Handbook to unpack how dual coding can be used with mini-whiteboards to make student thinking visible and strengthen understanding.
Why Does Dual Coding Matter?
All five lethal mutations above look like dual coding because all five contain words and pictures. But simply presenting both doesn’t guarantee that students will meaningfully connect the verbal and visual representations.
Dual coding mutates so easily because the resource is the part we can see, so it becomes the part we focus on improving. We add icons, photos and colour to slides, believing we are “dual coding” the content. But what matters more is what students do with those representations: how they connect words and visuals, explain the relationship between them, and use one to make sense of the other. That thinking leaves no visible trace on a slide.
“Learning is a generative activity.”
The connection has to be built by the student. Give them a picture and ask them to put it into words. Give them words and ask them to represent them visually. Providing both representations makes the connection possible; generating one from the other helps build it. This is the generation effect with a specific target: students generate the representation they weren’t given.
👉 Read The Generation Effect for why what students produce themselves sticks better than what they receive.
Either direction works. The more important question is who is doing the work. Too often, it’s us: we explain, we show the diagram, we provide the visual. Words to picture, every lesson — generated by the teacher.
The five strategies below shift that work to the student. Two reverse the familiar direction, asking students to turn a diagram back into language. The other three keep the words-to-picture direction, but put the generation in students’ hands.
Providing words and pictures creates the opportunity for dual coding. Asking students to generate one representation from the other makes them build the connection for themselves. Provide the words and ask for the picture, or provide the picture and ask for the words.
There’s a study that tests almost exactly this. Undergraduates learned about the human circulatory system. Some explained a diagram in their own words; others sketched what they had learned from a text. In both cases, students generated a different representation from the one they were given. Other students stayed within the same format: they explained a text or drew from a diagram. A control group simply studied both words and diagrams. On a subsequent comprehension test, the students who generated across representations performed best (Jaeger & Fiorella).
So the takeaway isn’t “add an icon”. That’s an instruction — the kind of misguided thing that comes from a twilight INSET and ends up on a resource. Too often, CPD tells us what to put on the slide, but not what students should do with it. The more useful principle sits underneath it:
Words and pictures are the setup. The learning comes from what students do between them: generating the words from the picture, or the picture from the words.
👉 Read Strategies vs Principles for why techniques drift when the principle underneath them isn't understood.
🎬 Check out the latest DistillED Explainer video on Remembering below.
How Do I Make Dual Coding Work?
There are two jobs here. The first is to get the resource right: remove anything that competes for students’ limited attention and make the words and visuals as easy as possible to process together. Four simple rules do most of the work:
Rule 1: Words go inside the picture, not in a key underneath.
On a diagram of a plant cell, place “nucleus”, “cell membrane” and “cytoplasm” directly beside the relevant structures with leader lines, rather than putting A, B and C on the diagram and making students repeatedly look down to a separate key.Rule 2: Say it or show it, never both in the same code.
Display a timeline showing the sequence of events leading to the outbreak of WWI while verbally explaining the significance of each event. Don’t display a paragraph containing the same explanation and read it aloud.Rule 3: If the image doesn't carry information, cut it.
When explaining the structure of a volcano, use a cross-section showing the magma chamber, vent and crater. Don’t add a dramatic photograph of an erupting volcano simply because the lesson is about volcanoes.Rule 4: The visual stays up while students work with it.
Keep a diagram of the heart visible while students explain the route taken by blood through the chambers, valves and major blood vessels. Don’t remove the diagram and then ask students questions that require them to hold its structure in working memory.
Those four rules deal with the capacity side of the problem. They prevent three of the five mutations before they take hold. They don’t create dual coding; they protect the conditions in which it can happen.
The second job is where dual coding actually happens: putting the connection-building work in the students’ hands. The five moves below do exactly that. The first two take students in the direction we rarely ask them to go — from pictures to words. The final three keep the more familiar words-to-picture direction, but shift the work from the teacher to the student.
Strategy | Explanation | Example |
|---|---|---|
1. Ask Students to Explain the Diagram Aloud
| Put a diagram up with the labels stripped out. Give short thinking time, then have students explain it to a partner in full sentences. Listen for the vocabulary you taught; its absence tells you exactly what hasn't landed. Explaining aloud beat drawing when students learned from a video lesson (Fiorella et al., 2020). | "Look at the diagram. In thirty seconds I'll ask you to explain each stage out loud, in full sentences, using the words from the board." |
2. Blank the Labels and Ask Students to Supply Them
| The diagram stays visible and the language disappears, so recall has to start from the image. Note the difference from the vanishing visual: here you're withholding the words on purpose while the picture stays put. | "Same diagram, labels gone. Whiteboards up in ninety seconds with all six. No talking." |
3. Have Students Draw From the Text, Not the Board
| Students read the passage, close it, then sketch what it described. Rough is fine — boxes, arrows and stick figures. The thinking sits in deciding what goes where, not in the artwork. | "Read it once. Books closed. Now sketch what that paragraph described — you've got two minutes, and nobody's marking your drawing." |
4. Let Students Build the Organiser
| Hand out the empty frame instead of the completed one, and match the frame to the content: sequence, comparison, cause and effect. Students place their own material and decide what connects to what (Mayer et al., 2025). | "Here's the frame, here are your notes. You decide what goes in each box and which arrows go where. Be ready to defend one of your arrows." |
5. Peg an Abstract Idea to One Concrete Image
| Ask students to choose the concrete anchor rather than handing them yours, then hold them to the same one every time the idea appears. Weeks later, cue the recall through the image and make them supply the idea. Paivio called this the conceptual peg: a concrete image acts as a hook that drags the rest of the material back with it. | "Remember the image we use for this. Picture it now. Tell me what it stands for and why we chose it." |
What links all five moves is easy to lose in the detail, so it’s worth stating plainly. None of them improves the resource. Every one changes what the student has to do with it. That’s the whole argument of this edition: the words and pictures are the setup. The learning happens in what students do between them.
If you change just one thing this week, take the visual you were about to explain and ask your students to explain it to you instead.
— Jamie
If you want more:
👉 Read The Simple Model of the Mind — how working memory handles two channels at once
👉 Read The Generation Effect — why what students generate themselves beats what they receive
👉 Read Worked Examples — the case for showing before asking, and where the balance sits
👉 Read Fading Support — removing the scaffold before it starts working against you
👉 Get the Memory and Cognitive Load CPD Collection — the fuller case for how working memory handles words and images together
👉 Get the Attention & Hard Thinking collection — for designing tasks that make students do the thinking
👉 Get the Reducing Cognitive Load pack — the four guardrails above, applied across your resources
👉 Get the Explanation and Clarity CPD Collection — for the wider work of explaining with words and visuals together
📥 Free One-Page Guide
Dual Coding Effectively One-Pager
To help you put this into practice immediately, download the Dual Coding Effectively One-Pager — a practical guide to using words and visuals in ways that support learning. It breaks down what dual coding is, why it matters, four simple rules for designing resources, and five classroom strategies for helping students connect verbal and visual representations. Useful for your own planning, in coaching conversations, or during team PD.
