two women asleep while on break at work

Right Shift on the Night Shift

This study is one of the reasons I try to keep track of the brain science literature on top of my usual study of HF/E. Despite my weak background in the biological side of neuroscience, I have some experience in cognitive neuroscience, which helps.

Unilateral brain damage can lead to a striking deficit in awareness of stimuli on one side of space called Spatial Neglect. Patient studies show that neglect of the left is markedly more persistent than of the right and that its severity increases under states of low alertness.

Apparently, when you are transitioning in and out of sleep, or suffering from task-related fatigue (i.e. after vigilance tasks), or have weak sustained attention abilities, you may be surprisingly susceptible to an odd artifact of vision. Things on the left side of your visual field might shift to the right. Or you might not notice them at all.

This has serious safety implications as well as performance ones. If an object is coming at you and you reach up to block it, you can miss because of the misplacement. Response time also increases in general. The study also found premature commitment errors – responding to a stimulus on the left side of the visual field before properly evaluating what it is and what the appropriate response might be – again leading to increased errors.

They have some neuroscientific hypotheses for why this might happen based on specific brain regions that might be causing it. But I am more interested in the HF/E implications for performance and safety. Many of our target users are working long shifts, night shifts, in vigilance tasks, or various other sources of these very situations. Pilots, truck drivers, health care workers, manual laborers, night shift security, and on and on. Is this something we need to watch out for and design environments to account for?

Image credit: “Asleep on the job” by Photocapy used under CC BY-SA 2.0

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