Designing Out Distraction: Understanding Cognitive Workload

How the design of physical things, systems and spaces around us can help prevent overloading.

What is workload?

 Workload is a term generally used to describe what we “do” at work, or more specifically the amount of what we do. It embodies the idea that work is a burden or “load”. It is important to everyone in any business because humans have a limited capacity for sustaining that load; if the load is too high or too low, the work itself will suffer, people perform badly, and we make mistakes.

Workload has two main components:

Physical, which is more obviously observed, like digging a hole or painting a wall;

Cognitive (or mental), which is more complex and involves decision making, problem solving and creative thinking.

Cognitive workload, because you can’t ‘see’ it, is more difficult to measure and is impacted by a host of internal and external factors such as stress, tiredness, noise and lighting. Attention is often used as a unit of measure when it comes to cognitive workload. That is – a person’s capacity to attend to what’s happening in the world around them and to make good decisions about how to act or react.

Plot of situation awareness vs. cognitive workload (adapted from Endsley & Jones (1997)).

Why is it important to understand cognitive workload?

Cognitive Workload is fundamental to human performance. When cognitive workload is too high, we can become ‘overloaded’, resulting in us using coping mechanisms such as taking short cuts or skipping certain procedures because there is a lot to do in an inadequate amount of time. We panic and our ability to do the job and our performance, suffers. This can have serious consequences for system performance and safety (for both ourselves and others).

Importantly at the other end of the scale, human performance and human error are just as susceptible if cognitive workload is too low. Humans are better at detecting and reacting to frequently changing stimuli. Static or repetitive situations struggle to maintain our attention; we get bored and lose focus or in some cases we even fall asleep.

When we hear of mistakes caused by human error, this must have something to do with cognitive workload, either too much or too little?

Human error is often the term used to blame people for a system failure. It is often the symptom of poor design, and frequently results from excessive mental workload. History abounds with examples of accidents and disasters where human operators made mistakes or poor choices that were put down to human error, but where mental overload and ineffective system design was the primary causal factor.

Essam, Rojas et al, 2019. Multimodal Fusion for Objective Assessment of Cognitive Workload: A Review

So, part of understanding cognitive workload and performance is systematic?

 There are two types of design that can positively impact cognitive workload, or rather, help minimise the degradation of attention: Systems design and Environmental design.

Systems design thinks of humans as single channel processors. That is, they are capable of consciously and properly attending to only one thing at a time. People’s effectiveness and efficiency will decrease as the number of signals or task actions increases; they’ve “only got one pair of hands”, right? People tend argue that this is demonstrably not true, that they can hear, see, smell and feel all at the same time, or that they can multi-task. It comes back to attention – our unit of measure for cognitive workload. The value of the concept of single channel processing is that it forces the designers to realise that the sequencing and timing of signals and actions is critical.

Just as you need efficient system design, a flickering light or screen glare would surely have a significant impact on someone’s ability to remain focused?

Absolutely! This is where the Environmental design becomes key as the system designer should be aiming at attracting and holding the user’s attention (i.e. not distracting them). They do this be enabling them to perceive the right information from one source at a time and to focus their mental faculties on a single associated task.

No matter how well the system is designed, if there are environmental factors that distract the users, this will have an impact on performance and accuracy. The environment must be designed to facilitate and maintain focus on the tasks at hand and minimise distraction.

What’s the balance, and how can we get that right when designing systems or workplaces?

 This is incredibly difficult to determine. The designer must consider the individual’s capability, in the context of the task and in the context of the environment or circumstances in trying to avoid under or overloading them with mental workload.

However, in a practical sense, this is very hard to do when designing an entire system or working environment such as a control room or office. You have different people of difference capabilities performing a range of tasks.

So how do we measure workload?

We can carry out a number of activities such as observations, meetings with end users and analysis of their current and / or future tasks to understand their current working practices and potential risks moving forward. A baseline assessment is always beneficial to understand a starting point and is also a valuable tool to see progress made.

And how can we improve?

To ensure all of these factors are taken into consideration when designing a system, it is vital that a full User Centred Design (UCD) approach is used. This means the people who will be using the system are involved in the process from initial concept, all the way through to the final design and implementation (essentially from start to finish).

The end users will be able to inform the designers throughout the process on aspects that currently or could affect their ability to carry out their job roles in the future such as current or potential environmental factors and cognitive workload challenges.

If we can never please everyone, then what’s the point?

When we say distraction, we mean anything that attracts a person’s attention away from the task in hand. It could be an interrupting signal or message, another competing task, co-workers chatting, interference such as noise or lighting problems, discomfort because of heat, cold or draughts.

What does the design of a working environment need to include to optimise performance and improve comfort and enjoyment?

Designing to minimise distraction should focus on optimising features that help people to do their work efficiently, balanced carefully with avoiding the creation of a boring space. There is no one-size fits all approach.

User representatives should be heavily involved in the design of work areas, desks and workstations because it is at these where most work is done and the users themselves know most about the work they do and what can support them in doing it. Handing some ownership of the design in this way to the occupants of the workplace involves them in making it work well, whilst gaining their buy-in. The design should help users to complete tasks efficiently, but also include for flexibility to evolve with future needs.

Flexibility and control of certain conditions is also key. For example, being able to adjust light levels (artificial and natural), temperature and air movement within comfortable ranges helps to optimise comfort. In addition to controlling fundamental factors like light, noise, temperature and air movement you can aim to enhance enjoyment of the space. Co-creating the space will result in a more successful (and well liked) design.

By bringing the end users along on the journey, gives them the ability to help influence the design and feel part of the decision-making process.  It also reduces the risk of a system and space being developed that simply doesn’t meet the user’s needs / requirements. This in turn, enables the end users to carry out their tasks more efficiently and with more enjoyment, which greatly reduces the risks of human error and improves overall efficiency.


Chris Avis


  1. Hi, great article, I am currently carrying out some research into reducing cognitive load in Early Years digital maths activities and I have discovered that ensuring children are ‘in learning mode’ prior to engaging in the activity is key to retaining the learning.
    Have you found any data relating to users being conscious of applying focus before carrying out a task and the success in completing the task?
    It would be great to hear your thoughts

Leave a Reply

Your email address will not be published. Required fields are marked *

14 − 9 =