Working Memory Model: Capacity & Explanation

Instructor: Andrea McKay

Andrea teaches high school AP Psychology and Online Economics and has a Masters degree in Curriculum and Instruction.

Memory is an important aspect of what makes humans unique. In this lesson, you will learn about working memory and how it helps us process information.


Can you remember your first birthday party? How about what you ate for dinner yesterday? Why do some memories seem solid and reliable while other memories are foggy? Studies in memory are important because our memories shape the people we are and the person we become. Psychologists often study how memory works in order to understand ways to improve memory and help those with memory disorders.

A Model of Memory

Many psychologists define memory as learning that has persisted over time, leading to a somewhat permanent change in knowledge. In a basic sense, memory works like a computer flash drive in three ways. We first encode and store information on a flash drive, and then we retrieve that information later, like we do when we pull up a file for an assignment. But perhaps memory is more prone to errors in all three areas of input, storage, and output.

Our memories work like a flash drive in which we input, store, and retrieve information.

In order to remember something, we must first encode that information. Encoding is how we process incoming messages. We first encode information coming in through our senses, as long as we are paying attention to those messages. This is known as sensory memory, or immediate but fleeting information that comes through our senses.

We cannot encode what we do not pay attention to, and in that way our memories are fallible. Our focus is limited, so we miss many messages that do not need our attention. Can you describe every detail of a dollar bill? Even though you've seen a dollar bill many times in your life, you will likely miss much of the detail because you did not encode the information.

Once the information is successfully encoded, it becomes part of either our short-term or long-term memory. Short-term memory is information that is held briefly and then is forgotten. Today, psychologists refer to short-term memory as working memory because it is believed that this type of memory involves a more active level of processing than just catching incoming signals.

What Is Working Memory?

Working memory can refer to information that is stored briefly while being encoded, and it can also refer to information that we retrieve from long-term memory. For example, if we hear a new phone number that we need to call, our working memory holds that number briefly while we dial the number, but typically that new number does not make it into our long-term memory. We don't usually walk around thinking of our best friend's phone number, but if it's stored in our long-term memory, we can bring that information into our working memory when needed. Both examples highlight the active processing involved in working memory.

The capacity of working memory varies per individual, but psychologists often refer to working memory capacity as seven, plus or minus two. A typical phone number is roughly the extent of our capacity. We can improve our storage capacity by chunking or grouping information into meaningful units. For example, many of us remember our social security numbers in small chunks of three. By chunking the information, we can commit more information overall into our working memory.

To encode and store information in our memories, we must first pay attention to incoming signals.

If items are completely unrelated however, our working memory capacity is only around four units of information. The memory achievements of world record holders are impressive when considering the limitations of normal working memory. The 2011 world record for memorizing a randomly shuffled deck of playing cards goes to Simon Reinhard, who memorized the order of the cards accurately in 21.19 seconds!

Working Memory Models

In 1968, researchers Richard Atkinson and Richard Shiffrin proposed a three-stage working model for memory. Sensory input (stage 1) became short-term memory (stage 2) and was either rehearsed and stored in long-term memory (stage 3) or was forgotten. The Atkinson-Shiffrin model was useful in demonstrating the effort required to move information into long-term memory.

By 1974, Alan Baddeley and Graham Hitch had expanded on the model of memory highlighting working memory. Known as the working memory model, Baddeley and Hitch stated that working memory has three active parts consisting of the phonological loop, visuospatial working memory, and the central executive component of memory.

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