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In this third edition of the CLT series, we're exploring the split-attention effect.
You’ll have seen it before: a beautifully presented diagram, with its labels detached and placed in a key at the side or below. Students’ eyes flick back and forth between the two, trying to match each label to the right part of the diagram while holding one in mind as they search for the other…
It might look clean on the page, but it makes learning unnecessarily hard.
⚗️ The Cognitive Load Theory Series: This edition is part of a new multi-part DistillED series translating contemporary CLT into classroom practice.
The Split-Attention Effect ← you are here
The Redundancy Effect
In this edition
📊 Do Now: Quick Poll!
Where do your students most often have to look in two places at once?
What Is the Split-Attention Effect?
Split attention happens when students have to combine two or more sources of information that have been separated, either in space or in time. The sources need to be combined to understand the material, so students must hold information from one in working memory while they search the other for its match. That searching and holding adds extraneous load, which is load caused by how the material is presented rather than by the content itself (Sweller, Ayres & Kalyuga, 2011).
The split-attention effect is the finding that students learn more when those sources are physically joined together, or presented at the same moment.
It was discovered by accident. In the late 1980s, Rohani Ahmad Tarmizi and John Sweller found that worked examples in geometry, studied by Year 8 and 9 students, were no better than problem-solving, which made no sense given how well worked examples worked in algebra. The problem was the layout. As in most textbooks, the solution steps sat underneath the diagram, so students kept looking back and forth to find which angle each line referred to. When the steps were written onto the diagram itself, next to the angles they described, the worked example effect returned (Tarmizi & Sweller, 1988). As Sweller put it in a recent podcast: "You can't look at the statement and the diagram simultaneously. You look at one, you've got to remember what's in the other one" (Thought Stretchers, 2026).
Split attention comes in two forms:
Spatial: the sources are in different places. A diagram with a separate key, a slide and a textbook, a method sheet and the equipment.
Temporal: the sources arrive at different times. You explain a process, then show the diagram, or the diagram leaves the screen while you're still talking about it.
In typical DistillED fashion, here's what the split-attention effect is, and what it isn't:
👎 The Split-Attention Effect IS NOT:
About Distraction → Split attention is not about distraction - it happens inside the task, when two things students need are in different places (Lovell, 2022).
A Reason to Add Labels to Everything → If one source makes sense on its own, the other isn't needed. Cut it, rather than integrate it.
Only About Words and Pictures → Two texts, two tables, or a sheet of instructions and a piece of equipment can split attention too.
The Same for Every Student → What helps a novice can get in the way of a student who already knows the content well.
👍 The Split-Attention Effect IS:
About Search → The cost comes from looking back and forth to match one source to the other.
Spatial or Temporal → Sources can be separated on the page or across time.
Strongest With Complex Content → It matters most when the content has many parts that depend on each other.
Mostly Fixable Before the Lesson → A few minutes spent rearranging a slide or worksheet can save students a lot of wasted effort.
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Why Does the Split-Attention Effect Matter?
Educator Ollie Lovell describes a Year 7 science lesson on the periodic table. The teacher presented a slide explaining what each part of an element’s box meant, while students had a printed periodic table on their desks. The explanation was clear, yet many students looked puzzled. Their eyes flicked from the board to the table and back again, trying to connect each point in the explanation to the part of the box it described.
After the lesson, Lovell and the teacher redesigned the slide around a single enlarged box for helium, placing each explanation directly beside the part it referred to (Lovell, 2020). As you can see below, nothing about the content changed. The problem wasn’t the explanation. It was the layout.
On the left, students hold each line of the explanation in mind while they find its match in the box. On the right, each label sits next to what it describes, so that search disappears. Separating two sources forces students to hold elements from one while they search the other, which adds to what working memory is juggling at once. Sweller and colleagues tie this in with high levels of element interactivity:
“In this manner, presenting information in a split-source format unnecessarily increases element interactivity resulting in an increase in extraneous cognitive load.”
The research supports this. A meta-analysis of 50 studies found a large overall benefit from integrating separate sources of information. The benefit was smaller for simple material and larger as the content became more complex (Ginns, 2006). A later meta-analysis of 58 comparisons also found a clear overall benefit, particularly for secondary students and paper-based materials. However, it could not confirm that the effect increased with content complexity because too few studies reported this clearly (Schroeder & Cenkci, 2018).
What students already know matters too. In one study, placing definitions of key words directly within a passage helped Year 5 students and less confident English learners understand what they were reading. But for adults and more confident English learners, the same approach made comprehension worse. They already knew the words, so the extra explanations became unnecessary information to process (Yeung, Jin & Sweller, 1998).
The message for classrooms is clear: Split attention is most likely to hinder learning when students have limited prior knowledge, the material is complex, and understanding requires them to mentally connect separate sources of information.
How Do I Reduce Split Attention?
Most split attention is built in before the lesson starts, in the slide, the worksheet or the method sheet. That makes it one of the easier CLT ideas to act on. The five steps below move from spotting it in your materials to helping students deal with it when you can't change the layout.
The goal isn’t to make complex content simple. It’s to remove unnecessary searching so students can focus their effort on understanding the content itself.
Step | Explanation | Example |
|---|---|---|
1. Spot the Look-Away Moments
| Walk through the task as a student would. Each time their eyes must move between two sources that need to be connected, mark it. If one source simply repeats information students can already understand without it, consider removing it instead. | Year 9 Geography: "Map on the slide, key on the handout, questions in the textbook. That's three places for one task, so I'll put them on one page." |
2. Put the Words Where the Eyes Are
| Write labels and solution steps onto the diagram. Put a source and its questions on the same page. Annotate the extract itself, rather than in a box underneath… There's a limit: pack too many labels into a diagram and it becomes hard to read, so number the parts instead. | Year 8 Maths: "Each step of the working sits next to the angle it's about, so you never have to look away from the diagram." |
3. Say It While They See It
| Keep the diagram up while you explain it, and point to each part as you name it. Explain in short chunks, each matched to what's on screen, rather than a long explanation followed by the picture. | Year 10 Biology: "Eyes on the left ventricle, here. As I trace where the blood goes, follow my pen on the visualiser." |
4. Link What You Can't Move
| Textbooks, past papers and equipment can't always be redesigned. When you can't bring related information together, make the connections obvious. Segment the text and use matching numbers or labels to show students what goes with what — an approach that can work as well as fully integrating the sources (Florax & Ploetzner, 2010). | Year 11 English: "Each colour in my notes matches a colour in the extract. Find the yellow line, then read the yellow note." |
5. Teach Students to Join It Up
| Show students how to join split material up themselves: number each chunk of text, put the same number on the part of the diagram it describes, and draw a line between them. Trainee teachers taught to do this performed better on transfer questions than those left with the split version, and were able to apply the approach to new material (Roodenrys et al., 2012). | Year 10 Physics: "Before you start, number each paragraph and put the same number on the part of the diagram it describes. Then draw a line between them." |
Science practicals are one of the clearest places to see this in action. A typical method sheet lists the steps on one page, with the apparatus diagram on another, and the equipment on the bench. Chemistry teacher David Paterson rebuilt his practicals as integrated instructions: one diagram of the set-up, with short numbered steps placed around it and arrows showing what moves where. Students generally completed practicals in good time, felt more confident, and the lessons ran efficiently enough to free up time for discussion. They still struggled with abstract or unfamiliar steps, which is a useful reminder that layout reduces wasted effort but doesn't replace teaching (Paterson, Education in Chemistry).
Ollie Lovell offers a rhyme worth sticking above the photocopier:
"Information that must be combined should be placed together in space and time!"
If you change one thing this week, open tomorrow’s slides or worksheet and look for one place where students have to look back and forth to connect two pieces of information. A diagram and its labels. An example and its explanation. A question and the source it refers to.
Pick one. Move the words next to the thing they describe.
— Jamie
If you want more:
👉 Read Element Interactivity: the last edition in this series, and why separating sources adds to what students must juggle
👉 Read Worked Examples: the strategy that led to the discovery of split attention
👉 Read Dual Coding: how to combine words and visuals so they work together
🎯 Teaching for Attention Playbook
My new Teaching for Attention Playbook is a 70+ page, evidence-informed guide that breaks down the science of attention and provides 6 practical strategies to support teachers.
📥 Free One-Page Guide
Cognitive Load Theory Unpacked One-Page Guide
To help you put this into practice, download Cognitive Load Theory Unpacked: a one-page guide to six strategies for managing what students must hold in mind, from checking prior knowledge to fading guidance as knowledge grows. Useful for your own planning, in coaching conversations, or during team PD.
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