The answer to this question is both very simple and incredibly complex. Simple because it’s very straightforward to demonstrate working memory in action; complex because to fully grasp the nature of working memory we really need to understand how it’s related to other types of memory. Let us then get the easy explanation out of the way by means of a simple question: How many windows does your home have? Now, don’t get up and count each one as you stroll around your home: stay where you are and count the windows in your mind. In the words one of the pioneers of working memory, Alan Baddeley, what you are doing as you carry out this task is creating a ‘cognitive workspace’ by ‘holding and manipulating information as required’ as you count. We can quite easily demonstrate working memory using everyday examples because we use working memory for everyday tasks.
Cognitive psychologists Alan Baddeley and Graham Hitch would investigate working memory through a series of verbal reasoning tasks. Participants would be shown a set of statements, like the ones illustrated below, and were then asked to decide if the statement was true or false. The time taken to respond could be seen as a measure of the effectiveness of the volunteers working memory. Sometimes, participants would also be asked to perform a secondary task simultaneously, such as repeating the the the out loud. The secondary task would, unsurprisingly, slow response times. The assumption here is that the secondary task increased load, making it harder to focus on the primary task.
But such demonstrations are only part of a much larger picture, and this is when things get complicated. Working memory is deeply intertwined with other cognitive processes such as attention, as well as higher order cognitive systems, known as executive function. Executive function includes a number of interconnected abilities, including any cognitive ability that involves the control of other simpler abilities, one of which is working memory (see below).
One of the major issues we face when getting to grips with working memory is that for decades researchers have occupied themselves with looking at their own particular area of memory. This means that one researcher might investigate long-term memory, another short-term memory and a third working memory and not always are the fruits of this research used to attempt a grand unifying theory of memory, so to speak. In addition, while cognitive psychologists investigate memory using laboratory-style experiments, neuroscientists investigate the living brain as it learns and recalls information. Others still, study individuals who experience severe memory deficits due to, for example, brain trauma or infection. It’s then very difficult to map findings from brain studies onto cognitive models. However, studies have found that working memory activates fronto-parietal brain regions, including the prefrontal, cingulate, and parietal cortices. More recent findings also implicate the role of subcortical regions, such as the midbrain and cerebellum. So when people are using their working memory, we can trace that action in the brain, even though there isn’t a specific working memory region.
Working Memory or Short-term Memory?
The name, working memory, was chosen to highlight its function; we do things in working memory, we manipulate the image of our home, keep a tally of the the number of windows and continually access other aspects of our memory to complete the task. Simply put, this workspace is our working memory. But is working memory synonymous with short-term memory? Furthermore, aren’t we also using long-term memory to count our windows?
Forsberg, Adams and Cowan describe working memory as ‘a system or set of processes, which keep temporary mental representations available for use in thought and action’. Cowan views working memory as ‘including short-term memory and other processing mechanisms that help to make use of short-term memory’, while Engle (2002) describes working memory as only referring to the attention related aspects of short-term memory. It’s clear, therefore, that working memory and short-term memory aren’t completely distinct from each other, but how they relate is often dependent on the theoretical view you adopt, but it certainly includes aspects of attention.
It’s hopefully easy to understand why working memory is important. When we carry out mental arithmetic, read a book or follow a set of instructions, we need to have a small amount of information readily available so that we don’t lose track of what we’re trying to do. Working memory is, therefore, an aspect of short-term memory even though how they actually relate to one another isn’t fully understood and there are a number of different views on this. However, just like short-term memory, working memory is limited and, as Forsberg, Adams and Cowan have stressed, ‘these limitations are important’ (2021).
A little bit of history
The term working memory first entered the research literature in 1960. In Plans and the structure of behaviour, Miller, Galanter and Pribram wrote ‘… we should like to speak of the memory we use for the execution of our Plans as a kind of quick access working memory.’ They continue, ‘When a Plan has been transferred into working memory, we recognise the special status of its incomplete parts by calling them intentions’ (p.76). The authors, however, don’t expand on this concept fully. George Miller is perhaps best known for his 1956 paper on the capacity of short-term memory, where he proposed that short-term memory can hold between 5 and 9 (7 +/- 2) pieces of information. More recently, however, Cowan, estimated this number as closer to 4. It’s generally assumed that these limitations also relate to working memory. These are the important limitations previously mentioned by Forsberg, Adams and Cowan.
We once again see the term working memory eight years later in the 1968 paper by Richard Atkinson and Richard Shiffrin, this time in relation to their multi-component model of memory. ‘The short-term memory is the subject’s working memory; it receives selected inputs from the sensory register and also from the long-term store’ (p90). It’s likely that Atkinson and Shiffrin borrowed the term from Miller, yet they don’t use the term in the same way as current researchers. The short-term working memory described by Atkinson and Shiffrin is little more than a static store used for simple rehearsal and transfer of information into long-term memory. It would be left to Baddeley and Hitch to add the dynamic nature as part of their own working memory model and attempt to clarify exactly what working memory is, as well as the function it serves (I’ve written about the model is some detail elsewhere).
Limitations generally include those related to capacity and duration. Incidentally, these two aspects of memory are also the ones used to distinguish between long-term memory and short-term memory, so long-term memory has limitless capacity and potentially indefinite duration while short-term memory has a capacity of around 4 items (Cowan) and a duration not exceeding around 30 seconds. Whether information in short-term memory decays over time or becomes the victim of interference from earlier and later information is one of the big unanswered questions of memory research, so I’ll leave that one alone. When we attempt to process more information than working memory can cope with, we increase the load on the system and any task becomes increasingly difficult; the cognitive workspace becomes too cluttered. If I’d asked you to count the windows and the doors in your home, chances are you’d choose to count, say, the windows first and then the doors; you’d know instinctively that trying to do both at the same time would risk overloading your limited mental resources. Similarly, if we’re sitting in a cafe reading a book, we’re going to find it hard to focus on the narrative if the couple at the next table are having a heated discussion; our attention will constantly flick from one stimulus to another. This latter example also highlights the role of attention in working memory, an area of research that is only just beginning to bear fruit. Interestingly, during the early days of cognitive psychology it was attention and not memory that occupied researchers, so much so that the Atkinson and Shiffrin’s multi-component model was based on the a model of attention proposed by Donald Broadbent, one of the early pioneers of the cognitive approach.
Getting past working memory limitations
Several methods have been development in an attempt to work around limitation problems, including chunking and mnemonics and models of instructional design (e.g. Cognitive Load Theory, Load Reduction Instruction). But, as Cowan points out, there is still a great deal we don’t know about working memory. He describes research as an upwards spiral; we make progress but still go around in circles. We still don’t know why there are limits on capacity and duration and we still don’t really know why we forget. Nevertheless, based on what we do know (or what currently appears to be the case) we can apply strategies that help to ease the load. To conclude, I’ll leave you with this from Cowan: