Why Some People Have “Two Left Hands”

There's a lot of variety in how skilled people are in doing complex tasks like handcrafting, wood carving, or drawing with their hands. While some people are good at knitting a beautiful sweater or drawing a photorealistic portrait of their pet, others are incapable of even much simpler tasks.

This difference in skill, of course, is driven to a large extent by training. Somebody who knits or draws a lot typically gets better with time than someone who never trains a specific skill. Still, training isn't everything. Some people can try as much as they want, but they always seem incredibly clumsy.

It is sometimes said that clumsy people have "two left feet"—but is there scientific evidence for something like “having two left hands”? Let’s have a look at the science of handedness to find out.

The Science of Handedness

When thinking of handedness, most people think of left-handedness and right-handedness. But did you know that there are more types of handedness than just these two?

Essentially, there are two ways somebody’s handedness can be determined:

1. Hand preference: The hand somebody subjectively prefers to write, draw, or do other tasks with their hands. This is assessed by a questionnaire. People are simply asked which hand they prefer for several activities such as writing or drawing,
2. Hand skill: Objectively measured skills with both hands. This can be assessed with reaction time tasks. For example, in the peg board task, people have to transfer little wooden objects into holes in a board with both hands separately while being timed.

For hand preference, three forms exist:

1. Left-handedness: The person prefers the left hand for writing and other activities.
2. Right-handedness: The person prefers the right hand for writing and other activities.
3. Mixed-handedness: The person prefers the left hand for some activities and the right hand for others.

In contrast to hand preference, hand skill is typically determined individually for each activity and not across many different types of activities. Here, also three forms are commonly distinguished in scientific studies:

1. Left-handedness: The person is faster and more accurate with the left hand.
2. Right-handedness: The person is faster and more accurate with the right hand.
3. Ambidexterity: The person is equally fast and accurate with both hands.

But what about people who are equally slow and clumsy with both hands? Is there a handedness category for them, too?

The Scientific Mystery of Ambisinistrality

The term for the opposite of ambidexterity is ambisinistrality. The term “ambidexterity” comes from the Latin root “ambi-," meaning “both,” and “dexter,” meaning “right.” The term “ambisinistrality” is an analog term, with the second part—“sinister”—indicating “left.” Therefore, it means “both left” and refers to the idea that since most people are right-handed, they are clumsier with the left hand. So ambisinistrality literally translates to having “two left hands.”

Ambisinistrality is somewhat of a scientific mystery; while several websites mention the term, scientific evidence for its existence is extremely rare. Using the scientific database PubMed, which contains millions of biomedical publications, I found exactly one study on ambisinistrality and it is several decades old.

In 1978, John I. Todor and Thomas Doane from the Department of Physical Education at the University of Michigan published a study entitled “Handedness and hemispheric asymmetry in the control of movements” in the Journal of Motor Behavior (Todor and Doane, 1978).

The scientists tested 20 men and 30 women with a tapping task to determine hand skills. They had to tap two targets alternately with a hand-held stylus as fast as possible. In different trials, the size of the targets varied from small (0.64 cm) to medium (1.28 cm) and large (2.54 cm). Smaller targets were harder to hit. This was done for both hands separately.

To determine hand skill, the number of correctly hit targets for each hand was compared. People that were better with the right hand were classified as right-handed and people that were better with the left hand were classified as left-handers.

Seventeen right-handers were clearly better with the right hand (left-handers were for some reason excluded from further analysis). Moreover, 33 “ambilateral” participants were not better with either hand.

Left Brain - Right Brain Essential Reads

Developing Extraordinary Abilities Through Savant Syndrome

The Difference Between Mixed-Handedness and Ambidexterity

Now, the scientists did something interesting: They compared the performance of the ambilateral participants with that of the right-handed participants. Those who were as fast and accurate with both hands as the right-handers with their right hand were classified as ambidexters. These were 21 people, a surprisingly large number which may be explained by the fact that the task was quite simple. For writing, a lower number would be expected.

The remaining 12 participants performed, with both their hands, about as well as the right-handers did with their left hands. Thus, the scientists classified them as ambisinistral.

Having “Two Left Hands” May Be More Common Than You Think

So yes, there is at least some (very old) evidence in a very small sample that ambisinistrality does indeed exist, but it's clear that larger studies should be conducted by scientists. Still, the percentage of ambisinistral people in this rather simple task was quite high (24 percent). Thus, if you know anyone who feels that they have "two left hands," it may comfort them to know that it may be more common than people think.

Facebook/LinkedIn image: Nicoleta Ionescu/Shutterstock