Your fighter is twice as likely to be left-handed as your wizard, but your wizard is less likely to have epilepsy.

Dr. Eric Lis is a physician, gamer, and author of the Skirmisher Publishing LLC sourcebook, Insults & Injuries.

Your fighter is twice as likely to be left-handed as your wizard, but your wizard is less likely to have epilepsy.

Handedness, the tendency for humans to favour one hand over the other, is a funny thing that modern science doesn't understand as well as one might think. For much of history, being left-handed was seen as an inherently bad or wicked thing. Fortunately, modern society no longer believes that sort of thing to be true, although left-handed people tend to be painfully aware that there's still a societal bias towards right-handed people. While handedness may no longer be correlated with evil, it remains associated with a number of other factors, both good and bad. Much as we'd like to claim otherwise, no one has a great explanation for why.

Handedness is very much neurological, and the brain has a sort of "handedness" of its own. The left and right hemispheres of the brain tend to be stronger at different tasks. For most people, the left side of the brain tends to be stronger in logic, critical thinking, and reasoning, while the right side tends to be stronger in creative endeavours, appreciating art and music, and understanding emotion. In the vast majority of people, the left hemisphere is the more important side for language, and while this is also true for the majority of left-handed people, they're more likely than right-handed people to have their dominant language centre on the right side. Naturally, all these tasks can't really be split up so evenly; both side of the brain play a vital role in all of these functions and damage to either hemisphere can impair one's abilities. None the less, it tells us that there's a degree of laterality to the brain, and we know that this laterality is less predictable in left-handed people.

A left-handed person is flat out more likely to have a neurological dysfunction. Large volumes of work have strongly suggested that epilepsy, mental retardation, autism, dyslexia, stuttering, and general clumsiness seem to be more common in left-handed people. Could the higher rates of epilepsy and seizures explain why, for centuries, people believed that left-handed people were more likely to be demon-possessed? It's an interesting question that we can't answer. Being left-handed is by no means a sign of a bad brain, however. For some years, it was believed that left-handed people have lower intelligence, but this assertion has been disproven a number of times. In fact, left-handed people make up a disproportionate number of musicians, artists, and mathematicians, and you'll note that not all of these are tasks classically associated with the right side of the brain. No one has ever been able to explain why musicians are more likely to be left handed than, say, software engineers, but some people do argue that it could be related to the right side of the brain being the more "creative" side. Since a century of research has yet to come up with a way to actually measure creativity, this question remains hard to approach.

Another interesting thing seems to be associated with being left-handed: a proficiency in combat. There's a concept in the literature called the "fighting hypothesis," which makes the following argument: given that being left-handed is associated with some important negative health consequences, and given that we know it's strongly genetic, it should have been bred out unless it also conferred some reproductive or survival advantage. The hypothesis goes on to suggest that left-handed people are more likely to excel in combat, or at least, in the closest analogue in Western society: sports. A number of studies over the years have repeatedly demonstrated that while left-handed people make up about 10-12% of the population, they make up closer to 20% of a number of combat-like sports, notably boxing, karate and fencing. We don't see the same over-representation in sports such as cycling or rowing. A number of studies have also suggested that left-handed boxers are more likely to win a fight than right-handed opponents. The favourite explanation for this in the literature is what's called a "frequency advantage." The majority of right-handed fighters train against other right-handed fighters and can be caught flat-footed when fighting a left-handed fighter, whereas left-handed fighters also spend most of their time fighting right-handed fighters but have the same disadvantage as right-handed fighters against other left-handed fighters. The benefits of being left-handed shrink as more and more of the population becomes left-handed, which reduces the pressure for it to become a more and more common trait. Some work has also suggested that left-handed athletes may be more aggressive on average, but this is work that as yet hasn't been widely supported.

A study published last year specifically examined the relative representation in the Ultimate Fighting Championship, which is arguably the closest you can get to what a medieval fantasy melee might have looked like by virtue of a relative lack of rules and regulated fighting style, and found that there were twice as many left-handed fighters than would be predicted by the general population, although interesting, they were no more likely than right-handed fighters to win fights. The authors wondered if maybe the left-handed fighters only had an advantage at less professional levels, and that by the time one gets to a championship, one's opponents are ready for you and it takes more than one trick to get the better of them. 

More than four years ago, Dr. Eris Lis, M.D., began writing a series of brilliant and informative posts on RPGs through the eyes of a medical professional, and this is the one that appeared here on September 27, 2014. Lis is a physician, gamer, and author of the Skirmisher Publishing LLC OGL sourcebook Insults & Injuries, which is also available for the Pathfinder RPG system.