What is Cognitive Load Theory?

Trying to get more specific about what the theory can tell teachers

What is Cognitive Load Theory?

It's a theory that's referenced often by cognitive-science-education-research types, but I have trouble finding readable summaries of what the theory means for teachers. I often see references to the fact that working memory can only hold 5-9 items (or is it 4?), or explanations of intrinsic, germane, and extraneous load. I find all that pretty abstract and distant from classroom teaching. But I've learned a lot from the ideas behind Cognitive Load Theory. I want to try to give a summary of how I think about these ideas.

A First Experiment

John Sweller is the researcher who launched Cognitive Load Theory. His first major experiment on the topic was an interesting one. He gave participants number puzzles. They were given a beginning number, and a target number. In each step, they could either multiply by 3 or subtract 69.¹ For example, participants might start with 60, with a target number of 111. First you multiply by 3, then you subtract 69, and you're done. Sweller gave participants a set of these problems, with a catch: every problem could be solved by alternating multiplication and subtraction, either once or multiple times.

Most participants never figured out the rule. They used a trial-and-error approach, and he observed that the repeated multiplication and subtraction was so mentally taxing that they never noticed the pattern.

I find this study interesting, but to me it doesn't have much to do with working memory or intrinsic/germane/extraneous load. It's a reminder of a simple rule of teaching: students learn what they think about. If I want students to learn something, I should do my best to get them thinking deeply about it. In this experiment, participants were thinking about the step in front of them, not the steps they'd already done. It's not surprising to me that they didn't figure out the pattern.

Worked Examples

That experiment was in 1982. Cognitive Load Theory has led to plenty of other results since, and by far the most popular is the worked example effect. In short, a raft of studies has found that studying a worked example is an especially efficient way to learn. Here are a few worked examples for rearranging equations from a study:

Many studies have since been done on worked examples. I use worked examples in my teaching, and I find they are really helpful when I'm first introducing a new topic. A common teaching strategy is for the teacher to solve an example at the board or on a projector, asking questions as they go and having students copy the problem down. What are students thinking about while trying to pay attention to an example, copy it down, and listen to questions? It's hard to know. Giving students a pre-worked example focuses their attention. Other strategies that involve students trying to solve problems as they learn a new concept risk the student losing the forest for the trees. They end up paying attention to specific steps — similar to multiplying by 3 or subtracting 69 — and lose sight of the bigger picture. Worked examples are a good way to get students paying attention to the whole as well as the parts. Students learn what they think about, and worked examples help students think about the right stuff.

Fading

A strand of research related to worked examples is on fading support or completion problems. Rather than transitioning straight from a worked example to a full problem for students to solve, students are given partially solved problems that they must complete. One reason fading is helpful is that it's less likely a student will get stuck. If students can't get started on a problem, they aren't doing much thinking at all. Another is that some students skip over the examples. A worked example followed by a completion problem pushes students to go back and look more carefully at the worked example and pay attention to the different parts of the solution. Fading and completion problems are temporary scaffolds, designed to ease the transition between initial instruction and practice. The goal is to get students thinking productively about problems as soon as possible.

Attention

The worked example effect alludes to another part of Cognitive Load Theory related to attention. It's hard to pay attention to multiple things at once. Humans end up switching between those things, which isn't a good way to pay attention to anything. One result of Cognitive Load Theory is called the split-attention effect. The split-attention effect says that when presenting a diagram and text, the diagram and the text should be integrated together, rather than in separate places. A second effect is the redundancy effect. If students are listening to narration, they shouldn't also be reading text — though images related to the narration are fine.

Both of these feel to me like reiterations of "students learn what they think about." If a diagram and text are far apart, students will have trouble connecting the text and the diagram. They won't be thinking about how the text and the diagram are connected, and they won't learn as much. If students are reading and listening at the same time, they will struggle to pay attention to either and they won't think as deeply about the topic.

Expertise Reversal

I left something out earlier. The research on worked examples suggests that they are helpful when students are new to a topic. But once students gain knowledge, they tend to learn less from worked examples and more from solving problems themselves. In the research world this is called the expertise reversal effect: as students gain expertise, the effectiveness of worked examples vs problem solving is reversed.

What are students thinking about? When they're first learning about a topic, looking at a worked example and answering questions about how the example works or why a certain step is the way it is can focus student attention. A worked example helps students think hard about the big ideas of a problem, without getting distracted by all the details they have to think about while solving the whole thing. If I want students to solve a complicated equation, they will quickly get lost in the specific steps. A worked example helps them step back and see the bigger picture.

But once students are proficient equation solvers, I want to take those scaffolds away. I want those students thinking, "ok how do I solve this problem? Which problems is it similar to? Which tools can I use?" Here students are thinking about how to apply what they know. That's exactly what I want them learning once they've got the basics down.

The Dangers of Cognitive Load

I don't like a lot of the ways I see Cognitive Load Theory described because the implication often seems to be that cognitive load is bad. But what is cognitive load? I want students thinking hard when they're in my class. Isn't that more cognitive load? I realize you can justify it with the whole intrinsic, germane, and extraneous thing, but I find those confusing and unhelpful.² There are lots of places where I want to increase cognitive load. I don't want to just show students a worked example, I want to ask them carefully chosen questions to help students understand what they are looking at and how to apply it. I don’t want to show students a worked example for every single little thing, I want them solving problems on their own and applying what they know as soon as possible. The goal isn't to reduce cognitive load, it's to focus student thinking on the essential things I want them to learn. I don't want them spending all their time multiplying by 3 and subtracting 69, I want them paying attention to the patterns and the big picture.

The more I read about Cognitive Load Theory, the more I think it really is about that simple idea: students learn what they think about. My job as a teacher is to design learning experiences that get students thinking about the right stuff. It's true that working memory is limited, but that just means we can't think about ten different things at once. The limitation of working memory is a reminder that we need to focus student thinking on the essential ideas we want them to learn, not leave that learning to chance. I can try to define all the intrinsic, germane, and extraneous load in a lesson. I can get even fancier and use something called element interactivity to explain which load is good and which is bad. Or I can constantly ask myself: what are students thinking about, and are they thinking about what I want them to learn?

The First Experiment Again

Remember the experiment where participants either multiply by 3 or subtracted 69? There's a risk that reading this you're thinking, "well of course that wouldn't work very well. I would never do that." But that kind of thing happens in schools all the time. Students spend their time dutifully multiplying by 3 and subtracting 69, following steps while missing the bigger picture. The teacher walks around the room. From their vantage point it's obvious. Every student is solving the problems, so of course they've noticed the pattern. But the students haven't noticed anything. I don't mean this literally, we don't ask students to do that particular task. But that same phenomenon is happening in classrooms, where students lose the forest for the trees. I think that original experiment points to something profound about teaching. It's easy for a teacher, with all of our knowledge and the end goal in mind, to assume that students will learn something. It might seem like the learning is staring them in the face. But students only learn what they think about, and it's easy to do a lot of things in a lesson that dance right around the learning without thinking about the thing we want students to learn.

For me, the lesson of Cognitive Load Theory is both simple and complex. Simple: students learn what they think about. Complex: there are a million ways that students can end up thinking about something totally different than what we intend, losing the forest for the trees or not thinking at all because of the structure of the lesson. Cognitive Load Theory gives me a bunch of different examples of how that can happen, a bunch of mistakes to avoid, and a few suggestions for how to better structure my teaching.³

1. You can tell Sweller wasn’t a middle school teacher — no 69s in my classroom.

2. If you are introducing someone to the idea of Cognitive Load Theory, definitely don’t lead with “ok so there are three types of load: intrinsic, germane, and extraneous…” You’ve already lost them.

3. If you’d like to learn more about Cognitive Load Theory, Michael Pershan’s history/literature review here is excellent.