Why is Working Memory so Important for Learning?

“My problem is that I have been persecuted by an integer. For seven years this number has followed me around, has intruded in my most private data, and has assaulted me from the pages of our most public journals. This number assumes a variety of disguises, being sometimes a little larger and sometimes a little smaller than usual, but never changing so much as to be unrecognizable.” George Miller

Working memory is one of those things that seems to simple but which has profound implications for how learning happens. It’s also one of those things that I wish I knew about when I first started teaching, particularly the ways in which different aspects of instructional design can impact working memory. The strange thing about working memory is that despite its modest capacity, it exerts an outsized influence on all learning outcomes. It’s also one of those things that most people think they know how it works but it’s only relatively recently that we’ve understood the limits of our understanding.

In the 1950s, George Miller famously proposed his ‘magic number’ that the number of items we can hold in short-term memory is around seven, plus or minus two. This idea laid the groundwork for understanding cognitive capacity, but later research refined it further, suggesting that working memory is even more limited, closer to four meaningful chunks. Crucially, it’s not just a passive store, but an active workspace where information is held, processed, and manipulated in real time.

Then the concept of working memory became popularised in the 1970s as an update to the older idea of “short-term memory.” Instead of seeing it as a passive storage space, Baddeley and Hitch described working memory as an active system for processing information, which is crucial for reasoning, comprehension, and learning. Unlike long-term memory which can store vast amounts of information for decades, working memory is remarkably vulnerable to disruption. A simple distraction, emotional state, or even classroom environmental factors can dramatically reduce its already limited capacity, which is why phones are so disastrous for deep learning.

And working memory isn’t just limited by how much information it can hold, it’s also shaped by how well attention is managed. At the heart of this is what Alan Baddeley called the central executive: a control system that directs focus, switches between tasks, and suppresses distractions. In real classrooms, this means that even simple tasks can become unmanageable if students are under stress, distracted, or overloaded and again, this is why knowing about the science of learning is so crucial. Effective instruction, then, isn’t just about reducing load, it’s about supporting attention. Clear routines, minimal distractions, and predictable structure help preserve the limited attentional control that working memory depends on. One of the main reasons so many of us have questioned discovery learning approaches or ‘minimally guided instruction’ is that working memory gets overloaded so quickly without having developed knowledge in our long-term memory.

Another big development was Cognitive Load Theory which is really built around the limits of working memory. It distinguishes between different types of load: intrinsic (the complexity of the material itself) and extraneous (how the material is presented). Understanding the limits of WM is really key to creating effective learning environments. If I had to boil down CLT to one thing, it would be that instruction must be designed to manage these loads, or learning won't happen.

So understanding working memory isn't just a theoretical nicety, it's a practical imperative for effective teaching. This is why techniques like modelling, guided practice, scaffolding, and removing distractions all serve one purpose: they protect working memory. They help students devote their limited resources to the actual content, rather than wasting it processing irrelevant information.

Anyway, I made some new videos with Paul for our How Learning Happens online course where we briefly talk about working memory, I’ve posted a short preview here.