If you want to survive a duel, there are a number of methods available to you. One: don't get into a duel, you aren't an aristocrat in 18th century France. Two: send your second to get shot on your behalf. Three: let the other person point their pistol at you and shoot at you first.
While not the most attractive option, let's talk about option three.
Physicist Niels Henrik David Bohr, while watching Western movies, noticed that the hero usually drew his gun second, but always slew the villain, who drew first. Rather than a dramatic gimmick to make the good guy look even more righteous, he suggested that it might be due to our own initiated movements being slower than our reactions. He believed that the person who reacts to their opponent raising their gun may, perversely, have the advantage, being able to shoot before their opponent.
Taking a break from particle physics, the next day Bohr took his friends out to test the theory. As ominous as it must be to hear the sentence "Hey Gary, I've got a theory about who dies first in duels and I want you to come outside", Bohr sensibly took the precaution of using toy cap guns.
According to the anecdote, Bohr drew second on every occasion – he won every time, pointing and shooting at his opponent before they could do so to him.
Now, the word "anecdote" should be a big red flag here, plus the fact that Bohr acted as the reactor every time. It doesn't take a professor of any of the major sciences to figure out that Bohr himself could be the variable – maybe was just fantastic at killing, but somehow ended up in physics. Bohr was not conducting a serious experiment, and no data or paper from the experiment exists.
However, other scientists have looked into the phenomenon to see if there's anything to it.
"We wanted to know if there was evidence for these reactive movements being swifter than the equivalent proactive ones," Dr Andrew Welchman, a BBSRC David Phillips Fellow at the University of Birmingham, who led the research said in a statement from 2010.
"So we set up a competition between two people who were challenged to press a row of buttons faster than their opponent. There was no 'go' signal so all they had to go by was either their own intention to move or a reaction to their opponent -- just like in the gunslingers legend."
The team found that, on average, the participant who reacted to their opponent's movement rather than initiating the movement themselves gained a 21-millisecond advantage in their movement speed during the task. While they believed this conferred some advantage to the reactor, the team found that accuracy diminished in pressing the correct buttons. Their conclusion? It's useful to have these reactions, but it probably won't stop you getting shot.
"As a general strategy for survival, having this system in our brains that gives us quick-and-dirty responses to the environment seems pretty useful," Welchman said.
"21 milliseconds may seem like a tiny difference, and it probably wouldn't save you in a Wild West dual because your brain takes around 200 milliseconds to respond to what your opponent is doing, but it could mean the difference between life and death when you are trying to avoid an oncoming bus."
So why did Bohr find the opposite?
"He was probably just a very good shot."