Ines Vuckovic/Dose

Investigating middle school slumber parties’ greatest prank.

Our Middle School Mysteries series investigates childhood rumors you never bothered to fact-check yourself.

I have a limited tolerance for staying awake — as a kid I was always the first to fall asleep at slumber parties. Everyone knows the first person out is the first to get pranked. Back then, one of the most popular pranks was dipping a sleeping person’s hand in warm water to see if they’d wet the bed, setting them up for a lifetime of urine-related nicknames.

I managed to make it through middle school without ever getting pee pranked (let’s take a brief moment of silence for those who were less fortunate). But I’m curious to know if dipping someone’s hand in warm water really causes them to lose control of their bladder.

Let’s investigate.

The experiment

If you look the pee test up on YouTube — and I highly recommend you do — you’ll see the results are inconclusive: sometimes the test works, but more often, it doesn’t.

But in 2009, the TV show “MythBusters” put the entire matter to bed, so to speak. The show brought two test subjects to a California sleep lab, hooked them up to brain monitoring equipment and lined the bed with moisture-activated voice alarms. Once the volunteer reached deep sleep, the other volunteer snuck into the room and dipped the sleeper’s hand in a bowl of warm water. Later, they swapped places so the sleeper became the dipper and vice versa.

Neither volunteer wet the bed. But that doesn’t mean it’s impossible.

The power of suggestion

According to a 1996 Gallup poll, 25% of all Americans identify as superstitious. This means that one quarter of the country believes they can achieve good fortune by carrying a rabbit’s foot or by avoiding ladders and black cats.

Psychologists believe our expectations are powerful enough to influence the outcome of a specific occurrence. For example, if you know parties make you feel anxious and drinking wine makes you feel less inhibited, after drinking a glass you might find yourself feeling and behaving in a more outgoing manner. The wine didn’t make you more extroverted — but your brain believes it did.

The same theory holds true for the hand-in-water prank. Mental Floss posits that there’s an unconditioned response between hearing the sounds of running water and having to pee. They argue that dipping a hand in water might cause the brain to make a similar connection, thereby relaxing the bladder.

Mental Floss also suggests that “immersion diuresis” might be to blame for this phenomena. Immersion diuresis is when the body is covered in water and subjected to changes in pressure and temperature, resulting in urination. For immersion diuresis to work, however, the entire body would need to be submerged, so Mental Floss doesn’t give this theory too much credence.

The results

Both MythBusters and Mental Floss contend that not enough research has been performed to make a definitive ruling on whether or not the pee test works. So there’s only one thing to be done: Everyone step up and pee test a friend (or enemy) today.

The future of science depends on it.