How TikTok's Pupil Test Works, And What It Tells Us About Love ... - WHYY

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The videos go like this: Someone uses their phone to zoom in on their eye, and then thinks hard about a crush, a love interest, or even their current partner. If their pupil dilates, then they’re really in love.

To Helen Fisher, biological anthropologist, senior researcher at the Kinsey Institute, and chief science adviser to the dating site Match.com, the interest in a test like this is only natural.

“Of course, we all do want to know whether somebody is attracted to us, and here’s another way of figuring it out,” she said. “I think this TikTok thing is quite ingenious.”

Fisher hadn’t seen the videos before, but she thinks they may be on to something. “It’s beautiful the way the body works, you know, it really is. There’s so many ways that we let the world know who we are without language.”

When we’re attracted to someone, Fisher said, it prompts a chemical rush that’s actually part of our fight or flight response.

“What’s going on is that when you’re thinking about somebody that you are in love with, that’s triggering activity of feelings in the limbic system in the middle of the head, that’s sending signals up to the hypothalamus, pumps out norepinephrine and epinephrine or adrenaline. And what the adrenaline does is it controls the iris muscle of the eye, and as that becomes activated, it pulls the pupil to become larger,” she said.

For human beings, love is a life-or-death issue. The region of our brain that produces feelings of romantic love is called the ventral tegmental area — VTA.

“This little brain region, the VTA, lies right next to the factory that orchestrates thirst and hunger,” said Fisher. “Thirst and hunger keep you alive today; romantic love drives you to form a partnership and send your DNA into tomorrow.”

She said it’s not clear why some pupils dilate and some don’t in these videos. It could be something to do with how peaceful your partnership is, or how long you’ve been together. But she’s interested in learning more.

“I think somebody should go do it,” said Fisher. “Take older people who reported they’re madly in love and see what happens to the pupils!”

Though a person’s dilated pupil can be a tell-tale sign of attraction, it’s a pretty subtle clue. Many other creatures seem to express their willingness to mate much more openly.