Heads or tails? Study reveals coin-tossing landing side preference

Photo by Steve Smith on Unsplash

More often than not, fate hangs in the balance between two options, determined by our decisions or even a spontaneous moment that leads us to choose one over the other. But is there truly a favored side when it comes to making a choice, as in the case of coin tossing?

In the Philippines, one of the traditional methods for resolving ties, whether in party games or even national elections, is by using a coin toss.

Recently, in the 2023 Barangay and Sangguniang Kabataan Elections (BSKE), the age-old practice of coin tossing has once again revived as a decisive tool in knowing the outcomes of the race in different parts of the country.

One of them was Alex John Agabao who was proclaimed SK chairman in Barangay 7 in Casiguran, Aurora after three rounds of coin tosses.

In the world of coin tosses, where chance and unpredictability reign supreme, researchers have recently unveiled an intriguing revelation. It turns out that fair coins, the very embodiment of randomness, tend to display a subtle bias, consistently landing on the same side they started.

This surprising result comes from a study of 350,757 coin flips, shedding light on a tactic that could potentially give you a slight edge during a coin toss.

So, which side should be chosen?

According to the findings, which are detailed in a preprint study published on the arXiv database and yet to undergo peer review, individuals who observe which side of the coin is facing upwards before the toss can increase their chances of success to 50.8 percent.

The study was participated by 48 individuals who collectively flipped coins representing 46 varied currencies. Participants were then instructed to execute the classic thumb flip technique, followed by a catch in their hand. This way of flipping aimed to eliminate the impact of coins landing on flat surfaces, which could introduce additional variables such as bouncing or spinning.

Frantisek Bartos, affiliated with the University of Amsterdam in Netherlands, explained that their research was partly inspired by work conducted in 2007 by Stanford University mathematician Persi Diaconis, who was also a former magician. Diaconis’ model suggested the existence of a “wobble” and a slight off-axis tilt in the trajectory of coin flips performed by humans.

The crux of this bias theory proposed that when a coin is flipped by hand, it would land on the side facing upwards approximately 51 percent of the time. Bartos’ study confirms this, with a winning probability of 50.8 percent—a nearly identical figure.

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Although a mere 0.8 percent advantage may not seem substantial, Bartos likened it to the advantage that casinos hold over even the most “optimal” blackjack players. This newfound understanding of the intricacies of coin tossing not only adds an exciting dimension to an age-old game of chance, but also offers a fresh perspective on randomness itself.

Next time, you might want to reconsider a lot of times if it’s either a head or a tail.