Working memory: A user’s guide

One of the questions that I’m often asked about human factors is “why do people behave like they do?”, or to put it another way, “why do smart people sometimes do dumb things?”.  But the question should perhaps instead be “why do people think like they do?” . . . and how could errors in our thinking lead to poor human performance, or even an incident?

A key concept in understanding how we think is our Working Memory. There’s very little written about this aspect of “thinking” in relation to human performance in the workplace – and so in this article I’m going to introduce the concept of Working Memory, discuss why it’s important and provide some advice on managing it’s limitations.

My first degree was in psychology and I’ve spent the past 25 years since then convincing people that I’m not trying to read their minds, but here I am talking about thinking . . .

What is working memory?

Let’s imagine that our brain looks something like this – a black box (well, in this case it’s more like a black trolley):

Working Memory as a black box -

In this analogy, the brain is represented by a stack of networked 512GB iPads, all connected together. These iPads contain everything that we know, or have known – in other words, they represent our Long-Term Memory.

However, everything that we know isn’t in our mind at any one time – we can only focus on a few things. To continue the analogy, if that black box of interconnected iPads represents our brain, then what we’re thinking of at a single point in time can be compared to what’s currently visible on the screen of a single iPad. Just like those iPads we have a huge storage capacity, but all of that information can’t fit onto a single screen at any one time. What’s on that single iPad screen represents our mind, and just like that iPad, the surface area of our “mental sketchpad”, or working memory, is actually quite small.

When we’re making decisions, working out a tip, listening to a podcast, following directions, or dialing a phone number, we’re using a short-term memory system to store and process the information that we’re currently thinking about. This working memory contains the current contents of our consciousness.

Working memory operates like a sketchpad or desktop, allowing us to comprehend, retrieve and manipulate information in our heads – for example, when we multiply 12 times 17. Note that this cognitive system isn’t just about remembering – it’s also enabling us to process that information; a kind of mental blackboard. Working memory holds the contents of our thoughts, providing a surface on which we can place information. We then “think” by manipulating this transient information, combining it with other items or transforming it into something new.

Unlike our long-term storage, working memory is for things that are important to us right now – not next week, next month, or even 20 years from now. Psychologists refer to what’s in our mind at this moment as “the cognitive now”. Whatever activity you are currently involved with, the information that you need to perform that activity is in your working memory for a brief period, such as the words in this sentence.

Not all information in working memory is transient – if we rehearse the information enough, the memory can become more permanent, and so working memory can be a gateway to long-term storage.

Working memory and learning

Working memory is essential for learning and development, particularly in childhood, and is highly predictive of reading and writing success, as well as being closely linked to mathematical skills. Working memory has been shown to be a better predictor of learning than IQ; because it is an indicator of our ability to learn. As you might expect, there are individual differences in working memory capacity – those with poorer capacity may have difficulties with tasks such as reading, mental arithmetic and concentration. Unfortunately, children with poor working memories are often diagnosed as having behavioural or attentional issues (“He doesn’t listen to a word I say”) – working memory failures are often overlooked.

The limits of working memory

Our working memory – what we can juggle in our heads at any one time – is quite limited.  It is similar to what can be written on a small Post-it Note (but with writing that fades very quickly). Information in our working memory lasts anywhere from 2 to 30 seconds, unless refreshed through rehearsal, and therefore we use our working memory as a short-term buffer, supporting our ability to work with information.

The average person can take in, process, comprehend and recall approximately 5 to 9 bits of unrelated information in this memory at any given time. These could be digits, letters, words, or other units. This is known as the 7 +/-2 rule (recent studies suggest that it may be less). Although our brain can store a lifetime of experiences, we can only process a few thoughts at once.

Information can be “chunked” or organised into familiar or manageable units in working memory to increase capacity. For example, the security code for one of my previous offices was 1-9-7-4. For many people this would be four bits of information, but as this was the date that a key piece of legislation was published by this organisation, the employees of the building could “chunk” these four digits into the year 1974 – and so for them this became only one bit of information – an easy task for working memory.

I have previously written about Performance Influencing Factors, such as fatigue, distractions and stress, that can have an adverse impact on our task performance. Several of these factors exert their negative influence in part via working memory. Back to the analogy – when you expose those iPads to extremes of temperature, run them for a long time without an opportunity to recharge, or give them dozens of activities to do at once, their performance suffers. And just like those iPads, human performance degrades when you treat people the same way. For example, fatigue has an adverse impact on our ability to process information by decreasing the capacity of working memory. Chronic stress leads to a reduction in working memory performance. Also, working memory is one of our cognitive functions most sensitive to decline in old age.

Given that our working memory is a limited mental workspace and we can’t consciously process everything that’s bombarding our senses, we tend to take mental “short cuts”. Unfortunately, that’s when the gremlins sneak into our system and human performance suffers.

Design for success: Human Factors Engineering

Working memory is essential for thinking, reasoning, comprehension, problem solving and decision making – all key activities in a safety-critical or complex environment. For instance, decision-making requires us to have the relevant information “in mind” to make a decision, or to formulate a course of action. Not surprisingly, working memory failures contribute to incidents and accidents. A low working memory capacity can lead to people forgetting instructions, struggling with tasks involving simultaneous processing and losing their place in complex tasks.

Understanding the limitations of our working memory is helpful, because we can then design workplaces, equipment and activities around these limitations. The objective should be to design systems so that they place fewer cognitive demands on individuals. This is one of the aims of Human Factors Engineering (HFE) – the science of applying human factors knowledge to the design and construction of equipment, products, work systems, management systems and tasks.

There are several things that you can do to maximise the potential of working memory, and ensure that what’s in a person’s working memory is what’s actually required to support the task at hand. For example:

  • design the system so that patterns in data are made obvious to the user. This will enable them to group data or create “chunks” out of the information, making effective use of the 7 +/-2 limitation
  • when designing tasks or writing procedures, ensure that it’s not necessary to work with more than five chunks of information at any time (i.e. reduce information overload)
  • restructure multiple-step tasks into separate independent steps so that people can focus on one thing at a time
  • when presenting information to users for processing, increase the meaningfulness and familiarity of the material to be processed
  • reduce the length of sentences used in procedures and simplify the language
  • provide job aids such as checklists and diagrams that contain key information, to reduce the items that need to be held in working memory
  • make it clear what information is key for a task – so that the user knows what they need to hold onto, and what they can let go
  • reduce the amount of interruptions and distractions, as these eat into the amount of working memory available for tasks, or cause the temporary information to be lost
  • encourage people to write down key information during critical tasks, such as in the early stages of an incident (especially when workload, distractions and stress levels are high)
  • ensure that the work schedule provides opportunities for sufficient rest, and provide support to individuals to help them get effective rest and quality sleep.

I’ve distilled decades of psychological research into a short article; so my apologies to any cognitive neuropsychologists who might be reading this!  Now that you understand a little about how our mind works, I’ll discuss how it can play tricks on us in a future article.

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