Banner Default Image

Adding Reality To Usability Testing – How Do You Simulate Stress?

Adding Reality To Usability Testing – How Do You Simulate Stress?

about 2 years ago by Julie McEwan

Julie Blog

In order for usability testing to be useful it needs to be as realistic to the real-world scenario as possible. Who will utilise the product and what will be happening around them when they do? I remember well the rush of adrenaline and increased heart rate that comes hand in hand with an emergency and the effect this has on the body.

Medical devices are often used in a high-pressured environment, from an Automated External Defibrillator on an unconscious/unresponsive person to an epi pen for anaphylactic shock, these devices need to be used efficiently and swiftly. Sometimes the stress falls on the patient themselves, other times it may be a friend or family member or even a first responder. This stress or surprise is common in many environments where safety is a primary concern, for example rail and aerospace and the simulation approach for testing is similar.

In this week’s blog, I will look at how this ‘stress’ is applied in usability testing to make it realistic, whilst weighing up the ethical and moral obligation to protect study participants.

Stress can be both physical and cognitive so it is important that the study is designed to impose and test for the right conditions. The best source of information on this subjected is undoubtedly the group that use the device – from patients to doctors, surgeons to paramedics – it is important that interviews are conducted to understand the challenges and problems they face and how stress affects their use of the device. It can also be useful to conduct field studies with people who are not regularly in contact with such devices, under different stress scenarios, to see how this alters interaction and whether this highlights other stresses not already considered. This can then provide the basis for the usability study and how best to replicate the real-life scenario.

Types of Stress and Symptoms

Cognitive stress is mental stress and affects the ability to think clearly and how to focus and filter information whilst in this state. Physical stress covers factors such as strength, posture and dexterity abilities. The symptoms of either type of stress are very similar and include an increase in heart and breathing rate, a decrease in concentration, the dilation of blood vessels in the limbs, shaking of the hands and a decrease in short term memory capabilities.

So how are these simulated?

Cognitive Stress

Imposed Time Limits

Stress can be added by setting participants a set task and giving them a time limit for it to be completed, whilst also stressing that it needs to be completed accurately. Sometimes the extra pressure of an audibly ticking clock is included to add to this or even an extra bonus of a prize or some other accolade for anyone who finishes the task accurately within the time limit. For anyone that has ever watched Countdown, I think we can all testify as to the panic that the audible clock instils and how disruptive it can be to thought processes.

Cognitive Overload

Another approach is to give participants excessive amounts of information to consider during the task or to have them complete several unrelated tasks simultaneously. One study I read set a manual task and at the same time asked the participants to complete a word match assignment. They were given random words and were asked to categorise them into appropriate groups.


Research conducted within simulating stress as part of assessing aeroplane pilots training highlighted the importance of the element of surprise. The study, published in The International Journal of Aerospace Psychology, highlighted that performance of a task in a predictable situation doesn’t guarantee the same successful outcome if completed whilst under unexpected stress. The participants were advised that during the training there would be a series of simulated stalls of the engine at set points along the route and this was adhered to for the control group. For the test group, the stalls happened at random times (despite the same brief as the control group) and the flight crew were purposely distracted by researchers asking them unrelated questions immediately prior to the stall happening.

Physical Stress

Simulating physical stress usually focuses on affecting the level of dexterity that the user needs to affectively use the device. Even shaky or sweaty hands can suffice. To achieve this heightened stress state participants are placed under a little physical stress. This could involve lifting and moving objects of weight sufficient to exert physical energy and increase both heart and respiration rates.

The application of physical and cognitive stress is obviously essential in order to promote testing of real value. However, what are the ethical implications of this for those running the study? The wellbeing of participants is of top priority and the level of the stresses provided should not be excessive. Studies of this type generally involve the oversight of an independent ethics committee or institutional review board to ensure participants safety and of course, if adverse effects are displayed by anyone the scenario must be halted immediately.

People’s thought processes and actions in an emergency situation are hard to predict and it would be impossible for usability testing to be undertaken in every single possible scenario. However, the application of stress in a simulated environment gives insights to the safety and effectiveness of the devices use in the expected conditions. Allowing possible problems and potential improvements to be visible to the design team and be corrected as necessary; ultimately leading to better products and more successful outcomes for the end user.

More Blogs from Julie McEwan

Julie has written numerous interesting and well researched blogs on a wide range of topics related to Medical Devices and Human Factors.  Please click here to read more of Julie's blogs and here to find out more about Julie.