The look of love
Do your pupils dilate when you look at someone you like?
Sitting in a romantic restaurant and locking eyes with your loved one, you notice their pupils seem to get bigger. You might have heard somewhere that this means they like you, but is this true?
The science behind the myth
You might have heard of dopamine, the "happy hormone". This is produced when your body expects a reward, such as a slice of cake, or attention from a loved one. Dopamine also causes the pupils to dilate as a side effect. So yes, your loved one's pupils might be dilating because they feel rewarded by being in your presence.
A study in the 1970s revealed that heterosexual men are more attracted to women when the women’s pupils are dilated. Being shown two photos of the same woman with pupils dilated to different sizes, men found women with larger pupils to be more attractive and open. This is because they unconsciously associated the dilated pupils with the women being attracted to them.
Women, however, don’t respond the same way as men to pupil dilation. An experiment by Tombs and Silverman resulted in women preferring a range of different pupil sizes. They discovered that heterosexual women who admitted they preferred short term relationships with more promiscuous men were more attracted to pictures with larger pupils. Women who preferred stable, long term relationships were more attracted to smaller pupils. Maybe size does matter, after all!
Did you know…?
In the Middle Ages, women in Italy poured a drop of Belladonna in each eye. A chemical called atropine in the plant caused their pupils to dilate, replicating the natural pupil dilation that would come from attraction. Belladonna, also called Deadly Nightshade, means “beautiful woman” in Italian. While having the desired effect of dilating the pupils, the plant is also poisonous and caused other unsavoury reactions, including blurred vision, permanent blindness, and accelerated heart rate.
Why else might your pupils dilate?
Throughout the course of a day, your pupils dilate and contract with the changing light conditions. The pupil increases in size to let more light into the eye if you’re in the dark and gets smaller in size to prevent too much light getting into the eye if it’s bright outside. This movement is unconscious; like a heartbeat, it’s just something your body naturally does without you having to think about it.
There may also be medical reasons why your pupils are dilated. It is a symptom of medicines that are used to treat Parkinson’s disease, poisoning, and even Botox. Your pupils might also dilate as a result of taking substances such as LSD, cocaine, and ecstasy, as it relaxes the muscles in the iris that control the size of the pupil. More concerningly, if you suffer a head injury, you might find your pupils remain dilated. If you find this to be true, and can’t even make your pupils shrink in bright light, consider visiting your doctor.
So, is it true?
Yes, in a way, however we can't be sure that love isn’t the only thing that makes the pupils dilate. If you’re eating a romantic meal with your loved one and notice their pupils are dilated, it may just be that the candlelight is too dim and not enough light is reaching their eyes. Or it may be that they just really love the meal they’re eating.