If you’ve watched Western movies you’ll know that most of the time there’s a predictable pattern to shootouts: the villain draws his gun first, but the hero shoots quicker and wins (before blowing the smoke from the tip of the barrel.)

Ask most people why this is and they’ll guess it’s to tell a moral story: the hero is honor bound not to draw first and shoot a man before there is a proven threat, but prevails through his superior skills. That’s a worthy story but one that appears to stretch credibility.

Now science has shown that there is a more logical explanation why the good guy could win, albeit it rarely. A joint project by researchers in Britain, Germany, China and New Zealand, published in Proceedings B, the biological studies publication of the Royal Society, shows that in tests, the gunfighter who draws first is usually shot by their target before firing their own weapon.

To simulate the action of pulling and firing a gun, participants were put into pairs and asked to hold down the middle of three buttons with their right hand (button 1 in the picture below). The “firing process” involved letting go of button 1, hitting button 2, then button 3 and finally hitting button 1.

In each sequence there was a secret, variable minimum time before which button 1 could be released; if either participant started “firing” before this time an alarm sounded and the sequence was declared void. This delay was intended to make sure the participants were in a situation where one initiated and the other responded, rather than both simply aiming to fire immediately.

When comparing results, the researchers did not compare the two participants in each exchange as this would have been skewed by the simple fact that one might be inherently quicker than the other. (There could also have been a limitation on any left-handed participants.) Instead they compared how each participant performed in the initiator role compared with their performance as respondent. When there was less than 100ms between the two “shots”, it was assumed both had acted in the initiator role and the result was discarded.

The results showed that on average a participant took 20ms less time to complete the sequence when responding to their opponent rather than initiating the process. The bad news for honorable gunfighters is that on average it took 200ms for the respondent to react to their opponent and begin firing.

The main biological conclusion from the study is that planned and reactive movements are controlled by different parts of the brain and work at different speeds. This may help solve some of the mysteries of Parkinson’s disease where the disparity between the two types of action is much greater: in some cases a sufferer can catch a ball more easily then they can pick it up from a table.

The main geek conclusion, however, is that HAN SHOT FIRST.