Erratic pupil behaviour can indicate mental stress: study

There’s a saying that eyes are the windows to the soul, but researchers at the University of Missouri have found they’re also great indicators of a person’s stress levels.

The study found people show predictable patterns of pupil dilation when they’re performing simple and easy tasks, says Jung Hyup Kim, assistant professor of industrial and manufacturing systems engineering at the University of Missouri. But once people are compelled to multitask and assigned complex challenges, pupil dilation patterns become erratic and harder to predict.

Read: Stress, aging population driving up mental-health claims

For the study, Kim and University of Missouri graduate student Xiaonan Yang enlisted participants to work in a simulated oil and gas refinery plant control room and monitored their eyes through motion-capture and eye-tracking technology.

First, they gave participants simple tasks and monitored their pupillary responses, which showed predictable patterns of eye-searching behaviours. Then the researchers introduced unexpected changes such as alarms, spurring participants to multitask and engage in more complex tasks. They subsequently found the participants’ eye behaviours became more erratic, indicating mental stress, says Kim.

Read: Majority of Canadians suffering from a mental-health issue, sleeping disorder: survey

“When you look at the monitor of the heartbeat, you can see the pattern of the heartbeat,” he says. “That pattern, if you see a regular pattern many times, we know this is normal. But if that pattern goes irregular, then we see that something is wrong with your heart. Then they can look deeper and find the cause of the irregular heartbeat pattern.”

Similar to those of a heartbeat, erratic behaviour of pupil dilation can indicate mental stress, something for which researchers currently lack objective measurement tools, says Kim. “There are many ways you can measure physical aspects like how much a person walks or carries something, but there’s no way you can measure the stress level [of a person].”

Read: Workplace stress a leading cause of mental-health issues: survey

The study has large implications for companies that employ emergency communicators, office workers and factory workers who engage in regular multitasking, says Kim. “We hope this finding can give a better insight on how systems should be designed to avoid mentally overloading workers and building a safer working environment.”

Further study on pupil dilation may also give employers an idea of how much work an employee can manage before their performance is affected negatively, adds Kim.

The study was completed in a controlled environment, but Kim hopes to use portable measurement tools in the future such as small eye-tracking devices for the average worker to attach while they’re engaging in tasks. Doing so will allow employers from many industries to measure mental stress in their workplace, he says.