Is your stash running on fumes? Consider using this natural high - or h'eye - that doesn't require eating, smoking, or vaping. You only need a friend, a dimly lit room and silence. But beware: you might have some freaky visions.

Those are the results discovered by Giovanni Caputo, a vision researcher with Italy's University of Urbino. In his study, which was published in a 2015 issue of Psychiatry Research, test subjects paired up and sat facing each other in a dim room. They were told to keep quiet and avoid making any facial expressions while staring into each other's eyes.

It didn't take long for them to trip out: after ten minutes, 90 percent of participants said their partner's face became deformed, 75 percent claimed their partner became a monster, 50 percent said they saw parts of their own face appear in their partner's, and 15 percent said they saw a relative's face appear at some point during the experiment.

Caputo isn't exactly sure why they had these experiences, but he does have an intriguing hypothesis: the hallucinations are a "rebound effect" as the pairs drifted between reality and a dissociative state. In other words, staring at a person's eyes too long makes you lose grip of reality.

But Susana Martinez-Conde and Stephen L. Macknik of Scientific American have a different theory: the hallucinations are a warped form of "Troxler fading." In the 19th century, Swiss philosopher Ignaz Paul Vital Troxler discovered that when we stare at something for a long time, whatever is in our peripheral vision disappears.

The Scientific American writers think that staring at a person's eyes makes the surrounding face disappear over time, but the mind tries to fill that void with something by drawing on personal experience or the imagination. That might be why people saw parts of their own faces or their relatives.

If you want to try the experiment at home, but can't find a human guinea pig, you can use a mirror instead of a partner by following the steps to Caputo's previous study.

Working alone won't be as trippy, but you'll still experience the mind-bending phenomenon of "strange-face illusion." Think of it as an adult version of "Bloody Mary."

h/t Scientific American, IFL Science