The Science Behind Why Left Handed Pitchers Have An Advantage

From Sandy Koufax to Clayton Kershaw, left-handed pitchers have dominated the game of baseball at the major league level since the beginning. Their ability to control the ball through various pitches is unmatched and can lead to the discussion of how much better a left-handed pitcher is versus a right-handed pitcher. 

Traditionally, left-handed pitchers have an advantage over right-handed pitchers simply because most batters have not faced as many left-handed throwers in their lifetime to adequately adjust to seeing the pitches coming out of a left hand.

Left-handed pitcher wearing white jersey delivering a pitch

However, there is more than one way to look at this puzzle. The nurture argument states that simple statistics show batters generally face fewer left-handed pitchers. Therefore, they do not have as much practice hitting against them. But, there is also the nature argument, where the brain and its ability to decipher and discern spatial thinking favors those who are left-hand dominant.

The Nurture Argument For Left-Handed Pitchers Having an Advantage

For the nurture argument, simple statistics and common thinking can best explain why it appears left-handed pitchers have an advantage in baseball. In the world, around 10% of the population is defined as being “left-handed,” meaning this percentage of the population writes left-handed, throws left-handed, eats with their left hand, and so on. 

When it comes to sports, practice makes perfect; therefore, because there are fewer left-handed people in the world, there are fewer left-handed pitchers for players to practice against. (Source: Science Daily)

Along with this argument is the fact that most baseball players are accustomed to seeing the baseball coming out of a right-handed pitcher’s hand. The advantage left-handed pitchers have can simply be determined by the fact that most hitters have not seen as many left-handed pitchers.

Take a game of tennis, for example: with a majority of players being right-handed, serves tend to travel to the opponent’s left side. This means the opponent has to use their backhand swing, which is a notably weaker attack. But, if the opponent were left-handed, the serve would actually be going to their forearm attack.

The Nature Argument For Left-Handed Pitchers Having an Advantage

The nature argument is a bit more complicated and more scientific than the nurture argument. To explain the nature argument, a little background information on how the brain functions is necessary.

The human brain is split into two hemispheres: the left and the right hemisphere. The left side of the human brain controls the right side’s motor skills and the right visual field, while the right side of the brain controls the left side’s motor skills and the left visual field. 

But the most critical distinction between the two sides of the brain is their functionality when it comes to spatial awareness. The right side of the brain is mainly responsible for the spatial awareness of the person, along with the dimensions that a person sees.

Spatial awareness is important because, by definition, it is how well a person can be aware of their proximity to another person or object; this allows left-handed people to have a greater awareness of how people and things are moving in relation to themselves.

To tie things together in the nature argument, we have to study how brains vary in left- and right-handed people. Studies have shown that left-handed people and right-handed people actually do have different brains and use them in unique ways. 

Left-handed people tend to use the right side of their brain more than right-handed people. And, as we just mentioned, the right side of the brain is the side that tends to have more spatial awareness and dimension gathering. 

Therefore, left-handed pitchers have a spatial and dimension advantage over right-handed pitchers. 

Are Lefties or Righties Better at Pitching?

So how does the science behind the nature and nurture arguments stack up to actual baseball stats and are left-handed pitchers better than their right-handed counterparts? 

Statistically, right-handed pitchers tend to be better on a variety of levels than left-handed pitchers.

For one, when comparing the two different kinds of pitchers, right-handed pitchers tend to have an advantage when it comes to velocity and spin rate. These are two critical factors when it comes to how well a pitcher fares in a game (for example, a one mph difference in velocity averages to 0.28 more runs allowed per nine innings).

  • Most right-handed pitchers have an advantage over left-handed pitchers when it comes to velocity. On average, right-handed pitchers have between a 1.3 and 2.1 mph advantage over left-handed pitchers across various pitches.
  • The other important aspect of pitching is the spin rate (which is just how many rotations a baseball does once it is released from the pitcher’s hand). Again, right-handed pitchers tend to have the advantage: anywhere from 33 RPMs (revolutions per minute) to 117 RPMs.

Simply combine the velocity and spin rate advantage, and that is how right-handed pitchers have an advantage of about 0.60 RA9 (runs allowed per nine innings) over left-handed pitchers. 

The Platoon Advantage in Pitching

Another factor is the platoon advantage. As we described before, baseball players have generally seen more pitching from right-handed pitchers than left-handed pitchers. But, statistics have shown that batters tend to do better against opposite-handed matchups (left/right platoons), while pitchers tend to be better in same-handed matchups (right/right or left/left platoons). 

With this in mind, teams began to try to acquire more left-handed hitters to gain the “platoon advantage”; 40% of batters in the MLB bat from the left side. This means that left-handed batters have the platoon advantage 73% of the time, whereas right-handed batters only have the edge 29% of the time.

For pitchers, the platoon advantage means that right-handed pitchers have the advantage over left-handed pitchers (since right-handed batters are more common). Right-handed pitchers have the platoon advantage 53% of the time versus left-handed pitchers, who only have the edge 29% of the time.

This platoon advantage means that left-handed pitchers give up about 0.20 more runs per game than their right-handed counterparts. 

The Unfamiliarity Bonus for Left-Handed Pitchers

So far, we’ve covered that right-handed pitchers have the advantage when it comes to velocity, spin rate, and platoon advantage.

However, left-handed pitchers come out on top when it comes to what Five Thirty-Eight calls an “unfamiliarity bonus”, which is that hitters are not as familiar with the ball coming out of the left side of the pitcher. But how big is the “unfamiliarity bonus” for left-handed pitchers? In short, the answer is 0.80 runs per nine innings. 

Statistically, left-handed pitchers are 0.60 runs per nine innings worse than right-handed pitchers, just based on their velocity and deception of the pitch (spin rate). But, add in the platoon factor (0.20 runs per nine innings), and that is how much left-handed pitchers have as an advantage by simply being a southpaw.

Do Left-Handed Pitchers Get Paid More?

Overall, there is no distinct difference in salaries between a left-handed pitcher and a right-handed pitcher. Of the top starting pitcher salaries in 2020, six of the top ten salaries are for right-handed pitchers. For relief pitchers, the same number of right-handed pitchers (six) makes up the top ten highest-paid players. 


In the end, science and statistics show that left-handed pitchers do generally have a slight advantage over right-handed pitchers. Whether you look at the nature or nurture argument, the case can be made that left-handed pitchers typically have a distinct advantage, backed by both science and the nature of major league baseball.

Steve Nelson

I'm the owner of Baseball Training World. I live in Denver, Colorado and I enjoy playing baseball on two different adult baseball teams in the surrounding area.

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