The myth of heads or tails collapses: one side always has an advantage and those who know can take advantage

Are you used to playing games? heads or tails to fairly decide a dilemma or start a game? Be careful, there is more than just chance in this coin toss.

It has become for centuries – perhaps even for a few millennia – a simple solution to resolve small dilemmas or simply to know who was going to start a game. : hop, we throw a coin in the air by betting on the face which will be visible once it falls. The heads or tails is a very convenient and easy draw. set up.

This is used by everyone: for a decision to be made take with friends, to resolve a conscience issue, or even to keep the children occupied. And this is very common in sports. Even the referee Ben O'Keeffe used his skills. of a coin toss to organize the kick-off of France – South Africa in the Rugby World Cup…

We are all pretty convinced that coin tossing is a perfectly fair method, because the probability of coin tossing is completely fair. ensure that the coin lands on its side. Heads or tails is 50% for each. This is an absolute truth. scientist. However, recent research by František Bartoš and his University team Amsterdam are challenging this idea.

According to this study, which required 350,757 throws in 46 different countries, the coins actually have a higher probability of being released. tendency to land on the same side as than the one from which they were born. This discovery confirms a theory stated 15 years ago by a statistician and magician named Persi Diaconis, who suggested I think the coin toss was biased.

But why? In reality, during a manual throw, the coin does not rotate perfectly around a fixed axis as in a physics model. The launchers introduce, without necessarily knowing it, oscillations or "precessions" which cause the coin to spend more time in the air with the same initial face up. And this increases the chances that it will land on the same side as it did. than at the start.

The data from this new study therefore reveals a bias, although this can vary considerably from one person to another. the other. The bias can be enormous, of the order of 60% in favor of the right side. initial bias among some throwers, while others toss the coin with little (or no) bias.

The manner in which throwers create these biases does not Although this is not yet very clear, future research will be necessary to better understand this phenomenon, which relates to ballistics. It is also important to note that the coins do not show a bias towards the  stack" or the "face" apart from this effect.

All this raises in any case an interesting question: can knowing this bias benefit the pitchers? The researchers explored this bias. this possibility by focusing in particular on betting scenarios. And they cautiously think so. When the stakes are high, they therefore suggest hiding the starting position of the coin before choosing heads or tails, to avoid giving an unfair advantage to the player. one of the participants!