It’s a trope straight out of romance novels: the deep stare, the slow lean-in, and pupils that grow wide with desire. But unlike a lot of sexy pseudoscience, this one holds up—your eyes really do change when you’re aroused.Specifically, your pupils dilate. Not because of candlelight or camera flash, but because of what’s happening in your brain. When you’re turned on, your sympathetic nervous system—the same one responsible for fight-or-flight responses—kicks in. That surge can cause your pupils to expand, sometimes doubling in size. It’s part of what researchers call “the six F’s”: fight, flee, feed, fix, focus… and fornicate.A 2021 meta-analysis published in the Archives of Sexual Behavior reviewed data from over 1,200 people across sexual orientations and confirmed that pupil dilation tracks closely with sexual interest—especially in men. Heterosexual men’s pupils dilated in response to erotic images of women, while gay men’s dilated for men. Women’s responses were more varied: heterosexual and lesbian women both showed dilation in response to male imagery, and some heterosexual women also responded to female imagery.Your Eyes Do This Weird Thing When You’re Turned OnBut here’s the kicker: pupil dilation isn’t always about attraction. Your pupils also dilate when you solve math problems, listen to music, or anticipate a reward. They’re sensitive to light, stress, fear, pain, and even certain medications or drugs. Which means trying to read someone’s sexual interest based on pupil size alone is dicey at best.That said, there’s some fascinating research on how pupils play a role in connection. According to a study published in The Conversation, people’s pupils can sync up during emotional conversations or teamwork—something called “pupil mimicry.” That synchrony often reflects shared arousal states, emotional alignment, or trust. It might be part of why intense eye contact can feel so electric.Back in Renaissance Italy, women used drops made from belladonna (literally “beautiful woman”) to dilate their pupils, aiming for that wide-eyed, seductive look—even though the stuff was toxic. Today, we’ve swapped out poison for eye drops at the optometrist, but the fascination with dilated pupils hasn’t gone anywhere.So yes, your pupils say a lot. But they don’t say everything. Whether you’re in a dim room with a hot date or just solving algebra in your head, context is everything. And if you’re wondering whether someone’s into you, maybe skip the eye-gazing analysis and try asking instead.The post Your Eyes Do Something Weird When You’re Turned On—and Science Can Prove It appeared first on VICE.