Artificial intelligence can reveal your personality by tracking your eyes. It’s been said eyes are the window of the soul in that they reveal your feelings and who you are. Now one line of study says eyes reveal our personalities – simply by the way they move.

In a study by the University of South Australia, in partnership with the University of Stuttgart, Flinders University and the Max Planck Institute for Informatics in Germany, Dr. Sabrina Hoppe wrote that people with similar personalities move their eyes in similar ways:

Optimists, for example, spend less time inspecting negative emotional stimuli (e.g., skin cancer images) than pessimists. Individuals high in openness spend a longer time fixating and dwelling on locations when watching abstract animations, and perceptually curious individuals inspect more of the regions in a naturalistic scene.

Hoppe’s team of four researchers tested 42 females and eight males, a combination of students and staff of Flinders University, Helsinki – all around 22 years-old – to see whether eyes could predict four personality types of the Big Five personality traits. In other words, whether people — or machines — could tell ahead of time that users were agreeable (i.e., kind, sympathetic, cooperative, warm), neurotic, extroverted, or conscientious, and adapt their actions accordingly.

Participants were outfitted with an eye tracker and told to walk around campus for about ten minutes and to buy any item of their choice from any of the stores on campus. All this time, the eye trackers recorded their eye movement before, during and after they entered the store, and as they were making their selected purchases.

When participants returned, researchers gave them three surveys on personality types, with questions assessing their trait curiosity as well as their neuroticism, extraversion, openness, agreeableness, and conscientiousness.

As their paper reported, researchers found that “for the first time an individual’s level of neuroticism, extraversion, agreeableness, conscientiousness, and perceptual curiosity can be predicted from eye movements recorded during an everyday task.”

Some of the participants’ activities showed more reliability than others, though. So, for instance, you could more reliably tell personality from eye movement when students were shopping than when they were casually walking around campus.