What Dual Coding Actually Is
Dual coding is the practice of learning new information in two formats at once: verbal (words, spoken or written) and visual (a diagram, sketch, chart, or mental image). The idea comes from Allan Paivio, a psychologist at the University of Western Ontario, who proposed Dual Coding Theory in the late 1960s and laid it out in full in his 1971 book Imagery and Verbal Processes.
Paivio's claim was structural, not stylistic. He argued the mind runs two functionally separate systems for handling information. One handles language, the verbal system. The other handles imagery, the nonverbal system. The two are linked, but they store memories independently. When a word triggers an associated image, the idea gets encoded twice, once as language and once as a picture, in two different places in memory.
That redundancy is the point. A memory stored in two locations is far easier to retrieve than one stored in a single spot, because you have two possible routes back to it. Forget the words and the image can still cue them. Forget the image and the words can still cue it. Single-format learning gives you one route and one point of failure.
The practical version is simple: when you learn something, don't just read or hear the words. Attach a visual that carries the same meaning. It does not have to be artistic. A rough box-and-arrow sketch works as well as a polished diagram, because the memory trace comes from the act of building the picture, not from how it looks.
The Science: Why Two Codes Beat One
The evidence for dual coding is unusually deep because Paivio's original work has been replicated and extended for over half a century. Clark and Paivio's 1991 review in Educational Psychology Review, "Dual Coding Theory and Education," pulled the education-relevant findings together and confirmed the core result: dual-coded material is consistently more memorable than single-coded material. The advantage shows up across ages, subjects, and decades of experiments.
The most cited applied evidence comes from Richard Mayer's work on multimedia learning. Mayer's Cognitive Theory of Multimedia Learning extends Paivio's idea to instructional design, and its central finding, the multimedia principle, is blunt: people learn more deeply from words and relevant pictures together than from words alone. Across a series of controlled experiments, Mayer reported that learners who received coordinated words and pictures outperformed word-only learners by a median of roughly 89% on transfer tests, with a median effect size above one standard deviation. Those are the tests that measure whether you can apply an idea, not just parrot it.
Mayer and Moreno's 1998 experiments gave the mechanism a direct test. They found that people handle words and pictures through separate channels in working memory: when spoken words accompanied on-screen pictures, learning beat the version where the words and the pictures both competed for the eyes at once. That's exactly what a dual-processing model predicts, and it's why how you pair a visual with words turns out to matter as much as whether you add one at all.
Here's the underlying logic, laid out step by step.
| Stage | Single coding (words only) | Dual coding (words + visual) |
|---|---|---|
| Encoding | One memory trace, verbal | Two traces, verbal and visual |
| Storage | One functional location | Two independent locations |
| Retrieval cues | One route back to the idea | Two routes; either can trigger recall |
| Failure mode | Forget the words, lose the idea | One channel can recover the other |
| Transfer | Weaker; tied to original wording | Stronger; the image supports flexible use |
None of this requires you to be good at drawing or to own special tools. It requires that the visual and the words mean the same thing and sit close enough together that your working memory can fuse them.
Dual Coding Is Not "Learning Styles"
This is the confusion that sinks most people, so it's worth being direct. Dual coding does not claim that some learners are "visual" and others are "verbal." It claims the opposite: every brain has both channels, and every brain benefits when both fire at once.
The learning styles idea, the one that sorts people into visual, auditory, and kinesthetic types and tells them to study only in their "style," is a myth. Pashler, McDaniel, Rohrer, and Bjork examined it in a 2008 review commissioned by Psychological Science in the Public Interest and found essentially no credible evidence for the "meshing hypothesis," the claim that matching instruction to a supposed style improves learning. Study after study has failed to find the effect. It keeps circulating because it feels intuitive, not because it works.
Dual coding is the evidence-based cousin that gets mistaken for its debunked relative. The difference is the target. Learning styles is a claim about people: match the method to the person. Dual coding is a claim about information: present it in two formats for everyone. One has failed to hold up under controlled testing. The other has decades of converging evidence behind it.
If you have ever been told to "find your learning style," dual coding is the better replacement, and it applies to you regardless of what that quiz said you were.
Where It Fits Among the Evidence-Based Strategies
Cognitive scientists Weinstein, Madan, and Sumeracki grouped the most robust study techniques into six strategies in a widely cited 2018 review. Dual coding is one of them, sitting alongside methods Glasp readers already know well. Seeing the full set makes clear that dual coding is not a standalone hack; it stacks with the others.
| Strategy | What it does | Related reading |
|---|---|---|
| Retrieval practice | Recall from memory instead of rereading | Active recall |
| Spaced practice | Spread study across days, not one session | Spaced repetition for readers |
| Interleaving | Mix problem types instead of blocking them | Interleaving practice |
| Elaboration | Explain how and why, connect to what you know | The Feynman technique |
| Concrete examples | Anchor abstract ideas in specific cases | (see below) |
| Dual coding | Pair words with a meaningful visual | This article |
The strategies compound. When you draw a diagram of a concept (dual coding), then cover it and redraw it from memory (retrieval practice), then repeat that a few days later (spaced practice), you are running three of the six at once. Each adds a layer of durability. Dual coding's specific contribution is the second memory trace; the others control when and how you rehearse it.
Many of these techniques, dual coding included, feel harder than passive rereading while you do them. That friction is not a flaw. Robert Bjork's research on desirable difficulties shows that the effort of generating a visual, rather than just absorbing one, is part of what makes it stick.
How to Use Dual Coding When You Read
Reading is a verbal activity by default. Dual coding means adding a visual layer to it deliberately. Here are the methods that work, roughly from lowest to highest effort.
- Graphic organizers. Convert a section of text into a flowchart, a Venn diagram, a comparison table, or a hierarchy. This is dual coding at its most structured, and it doubles as an outline. A process becomes arrows; a taxonomy becomes nested boxes.
- Timelines. For anything with a sequence, history, a biography, the steps of a method, lay the events on a line. The spatial order becomes a second cue for the temporal order.
- Sketchnoting. As you read or watch, capture ideas as small drawings and labels instead of full sentences. The drawings don't need to be good. A stick figure and an arrow encode a relationship as well as a paragraph does, and faster to review.
- Concept maps. For dense, interconnected material, map the concepts as nodes and label the links between them. This forces you to make relationships explicit, which is both dual coding and elaboration.
- Margin sketches. The lightest-weight option. Next to a highlighted passage, draw one small icon that captures its meaning. When you scan the page later, the icon cues the idea before you even read the words.
The common thread: you are translating verbal input into a visual representation you build yourself. The translation is the work, and the work is what lays down the second trace. Passively looking at a diagram someone else made helps a little. Making your own helps far more, because the act of deciding what the picture should show forces you to understand the material.
This is also why highlighting is where it starts. A highlight isolates the verbal core of an idea, the sentence worth keeping. Dual coding is the next move: take that isolated sentence and give it a shape. The highlight tells you what to encode visually; the sketch does the encoding.
When Visuals Backfire
Dual coding is not "add pictures and win." Mayer's decades of experiments also mapped the ways visuals hurt learning, and ignoring those is how well-meaning study guides become cluttered and useless.
Three failure modes matter most:
- The redundancy effect. Presenting the same words as on-screen text and narration at the same time makes learning worse, not better. Both compete for the single verbal channel and overload it. Words plus a picture is dual coding. Words plus the identical words in another format is just noise.
- The split-attention effect. When a diagram and its explanation are physically separated, a chart on one page and its legend three pages later, learners have to hold one in memory while hunting for the other. That integration cost cancels the benefit. Keep the label on the picture, not in a distant caption.
- The coherence problem. Decorative images, stock photos, and "engaging" graphics that don't carry meaning add cognitive load without adding a memory trace. If the visual doesn't represent the idea, it isn't dual coding. It's clutter.
The rule that ties these together: the visual has to be meaningful, and it has to sit next to the words it explains, presented close in space and time. Get that wrong and you're not coding twice, you're overloading once. This is why sketching your own simple diagram usually beats importing a busy infographic: yours is guaranteed to be relevant, and you control where the labels go.
A Dual Coding Workflow With Glasp
Dual coding needs a reliable source of verbal material to convert, and a place to keep both the words and the visuals together. That's the workflow Glasp is built for.
Start with the verbal capture. As you read an article or a PDF, use Glasp's web highlighter to mark the sentences worth keeping. Highlighting is the filter: it strips a page down to the handful of ideas that deserve a second memory trace, so you're not trying to dual-code an entire chapter. Because Glasp supports multiple highlight colors, you can even pre-sort passages by the kind of visual they'll become, blue for anything that maps to a timeline, green for anything that becomes a comparison.
Then build the visual. Next to each highlight, Glasp lets you attach a note, so that's where the sketch, the mini-table, or the concept map goes. The highlighted sentence and your drawn version of it live side by side, which satisfies the split-attention rule automatically: the words and the image are never separated.
Video is a natural fit too. When you learn from a lecture or explainer, YouTube Summary pulls the transcript and key points so you have the verbal layer ready to convert into a diagram, instead of scrubbing back through the video to find what was said. The same move works on books: bring in your Kindle highlights and turn the passages you marked into visual summaries.
For a fuller treatment of turning captured material into durable notes, see how to take smart notes and, for video specifically, turning YouTube into study notes. Dual coding is the encoding step inside those larger workflows.
Common Mistakes to Avoid
Even people sold on the idea trip over the same few things.
- Copying someone else's diagram. Passively viewing a pre-made visual gives a fraction of the benefit of building your own. The generation is the mechanism. If you only ever screenshot other people's charts, you're barely dual coding at all.
- Making it too pretty. Time spent perfecting a drawing is time not spent learning. The research rewards rough, fast, meaningful sketches, not art. If you're choosing colors for twenty minutes, you've lost the plot.
- Coding trivia instead of structure. Dual coding shines on relationships, processes, hierarchies, and comparisons, the things that have a shape. A flat list of dates to memorize is better served by retrieval practice. Use the visual where there's structure to see.
- Confusing it with learning styles again. Worth repeating: you are not dual coding because you're a "visual person." You're doing it because two channels beat one for everyone, including you.
Avoid those four and dual coding becomes one of the highest-return, lowest-effort changes you can make to how you study and read.
Frequently Asked Questions
What is dual coding in simple terms?
It's learning something in two formats at once, words and a matching visual, so your brain stores it twice. One idea, two memory traces, in two separate systems. That gives you two ways to recall it later, which makes forgetting much less likely than when the idea exists only as text.
Is dual coding the same as learning styles?
No, and it's the opposite in an important way. Learning styles claims individual people should be taught in their preferred format, and that idea has repeatedly failed controlled tests (Pashler et al., 2008). Dual coding claims everyone learns better when words and visuals are combined, and that has strong evidence behind it. Dual coding is about the information; learning styles is about the person.
Do I need to be good at drawing to use dual coding?
No. The benefit comes from building the visual yourself, not from how it looks. Boxes, arrows, stick figures, and rough tables all work. A messy sketch you made beats a polished diagram someone else made, because the act of deciding what to draw is what encodes the idea.
Can dual coding ever hurt learning?
Yes, if the visual isn't meaningful or isn't placed next to the words it explains. Decorative images, identical text read aloud (the redundancy effect), and diagrams separated from their labels (the split-attention effect) all add cognitive load without adding a useful memory trace. The visual has to represent the idea and sit close to the related words.
How is dual coding different from just taking notes?
Ordinary notes are usually verbal, more words alongside the words you read. Dual coding specifically adds the visual channel: you translate the verbal material into a diagram, map, or sketch. It's the translation into a different format, not just the recording, that creates the second memory trace.
Which subjects benefit most from dual coding?
Anything with structure: processes, systems, hierarchies, sequences, and comparisons all map cleanly onto visuals. History timelines, biology cycles, cause-and-effect chains, and concept relationships are ideal. Pure rote lists benefit less and are better handled by spaced retrieval practice.
The Bottom Line
Dual coding is one of the best-supported ideas in learning science, and one of the most misunderstood. It isn't about being a visual person, and it isn't about decorating your notes. It's a structural fact: your mind stores language and imagery separately, and feeding both leaves two traces where reading alone leaves one.
The practice follows directly. Read for the verbal core, highlight the sentences that matter, and then convert the ones with structure into a diagram, timeline, or sketch you build yourself. Keep the visual meaningful and keep it next to the words. Stack it with retrieval and spacing, and the ideas stop slipping away.
You already do the first half every time you read. Glasp is where the highlighting, the notes, and the visuals stay together, so the second trace is always one sketch away from the first. Start highlighting what matters, then give it a shape.