I am part of the ten percent of the human population which is left handed. Simply by virtue of me being a southpaw, I am more prone to accidents and immune deficiencies, but the left and right hemispheres of my brain exchange information more readily, and I am naturally more creative due to right brain dominance. What is interesting, though, is that I am not left-handed across the board. I do many things right handed, but more on that later.
Studies have discovered that elevated testosterone levels in the womb are often what cause left-handedness to occur. Apparently the higher testosterone level slows the development of neurons in the left hemisphere of the brain, causing more development in the right hemisphere and a corresponding left sided body dominance. One gene (LRRTM1) has also been linked to left-handedness. Some left-handers like me have a cross-dominance, in which one hand is favored for certain tasks while the other hand is favored for other tasks. This is in contrast to a true ambidexterity, in which neither hand is favored over the other.
Here is how my particular hand dominance breaks down:
Write with left hand
Draw and paint with left hand
Perform injections with left hand
Eat with left hand (but can hold utensils with right hand)
Brush teeth with left hand (but can use right hand too)
Tweezers with left hand
Flatiron with left hand
Brush hair with either hand
Throw a ball with right hand (can’t do it with my left at all)
Use computer mouse with right hand
Play(ed) guitar right handed
Play pool right handed
Bowl right handed
Play darts with right hand
Kick with right foot
I am still not completely sure what this all means, despite having considerable training in science and medicine. It’s pretty fascinating to me, though. I would love to hear from people who might have a little cross-dominance.