Stress can cause someone to not be able to do tasks they are familiar with.
Under stress, people tend to do the same actions over and over, even if they don’t work.
Do as much research as possible to find out which situations in your product may cause stress. Including site visits and observing people interacting with your product and redesign as needed.
Even if someone is an expert at a well-learned task, performance stress may cause errors.
A little stress can help perform a task because it heightens awareness, but too much stress degrades performance.
The optimal amount of stress/arousal depends on the difficulty of the task. Difficult tasks require less arousal while simple tasks require more arousal to keep the user's attention.
If people are performing a boring task then you need to raise the level of arousal with sound, colors, or movement.
If people are doing a difficult task, then you need to lower the level of arousal by eliminating any distracting elements.
Slide 3
Tunnel Action
Tunnel action is where you keep doing the same task over and over even though it isn’t working.
Too much stress causes the user to be unfocused and have trouble remembering thus causing the tunnel action.
Don’t assume that people will use your product in a stress-free environment.
Men and Women may react differently to stress.
Performance stress may cause errors for experts. The higher the stakes the more pressure is on the user to perform well, causing errors.
See more information on the Yerkes-Dodson Law in the video linked.