Hand Dominance

Written by: Crista Parker, Occupational Therapist

I have been an OT for about 10 years and I have gotten one question the most throughout my years working with the pediatric population: “Is it important for my child to have a hand preference when she writes?”

The quick and easy answer is “ABSOLUTELY;” however, how the brain controls the body is a little more complicated. First, we need to understand the basic anatomy of the brain. The brain is divided into two parts, each containing a motor cortex and specialized areas of control. The right side (hemisphere) is typically associated with imagination, art awareness, and creativity. The left hemisphere is associated with logic, language, and reasoning. Each side of the brain has a motor cortex, which is the part that controls muscle movements of the opposite side of the body; so if the left brain is activated, the right side is moving. If the child is writing with the left hand, she is activating the right side of her brain for the motor task. Over time and with practice, this hemisphere that is routinely used for writing becomes specialized and “lateralized” to perform this task.  Much like learning to ride a bike with improvement of skill with practice, writing skills improve with consistent practice and activation of the same portion of the brain. Most people have a left brain lateralization (or specialization), which is why most write with the right hand—which also leads to the right eye and foot dominance.

A lack of lateralization (or specialization of one side of the brain) is called “mixed dominance.” There have been several research studies that are linking mixed dominance to decreased performance in academic settings, behavior issues, and sensory processing limitations. These difficulties are due to a “traffic jam” and disorganization of the information that is common when one side of the brain has poor lateralization or specialization. In a typically developing brain, when the left side is activated with the handwriting task, the right side is the supporting role and helps the incoming information get to the appropriate portion of the brain. With mixed dominance, there can be confusion of the information with the two sides of the brain competing against each other for the information—leading to confusion and disorganization. When this disorganization happens, more behaviors are observable and she may have difficulty with sensory regulation. Behaviors that can happen with lack of specialization by the brain are the following: quick to anger, emotional, obsessive-compulsive behaviors, decreased attention span, easily frustrated with lack of perseverance, easily distracted, or impulsive. Dr. Jean Ayres (the sensory integration expert) said, “If the two sides to the brain cannot work together to communicate, they both tend to develop similar functions.” Have you ever heard the saying, “Jack of all trades and master of none?” This can refer to the disorganization and lack of specialization that can happen in the brain if lateralization does not occur completely—which can slow down development and retrieval of information. It can also impact reading and comprehension as well. Interestingly, letter reversal, which is typically mastered by the end of 1st grade, can also be correlated to poor lateralization as well—mixing up “b” and “d” or “6” and “9.”

So the bottom line is that lateralization and specialization of one hand for handwriting is important—not only for handwriting but for other aspects of learning and behavior management. If you are concerned about your child’s hand preference, or lack of one, there are things you can do to help. Consider asking your pediatrician for a referral to occupational therapy. We can help by providing information on the following activities, depending on the child’s need: midline crossing, bilateral coordination, strengthening, coordination, visual motor, and handwriting. The number for outpatient pediatric occupational therapy is 573-632-5614.