True ambidexterity refers to the ability to use both the left and right hands with equal competence across all fine and gross motor tasks. This balanced skill level is an exceptionally rare trait. The vast majority of people exhibit a clear preference for one hand, known as handedness. Exploring the possibility of true ambidexterity requires an understanding of the brain’s organization, the various degrees of hand use, and the potential for skill acquisition through training.
The Neurological Basis of Hand Preference
The reason most people are not ambidextrous lies in cerebral lateralization, a fundamental principle of brain organization. This describes how specific functions are predominantly controlled by one of the two brain hemispheres. Motor control for the hands operates contralaterally, meaning the left hemisphere controls the right hand, and the right hemisphere controls the left hand.
For approximately 90% of the population who are right-handed, the left cerebral hemisphere is typically more dominant for fine motor control. This hemispheric dominance for hand articulation and skill is established very early in development, often observable in the fetus. Handedness is influenced by a complex interplay of genetic factors and non-genetic factors like environmental influences.
The neural pathways involved in motor control, particularly the corticospinal tract, also exhibit asymmetry in most people. This tract connects the cerebral cortex to the spinal cord, and in right-handers, the tract connecting to the right hand is often significantly larger. Ambidexterity is thought to be associated with less defined lateralization, resulting in a less biased connection to both hands.
Left-handers tend to show less pronounced brain lateralization for sequential movements compared to right-handers, activating a larger volume of brain areas. This less specialized organization makes the brains of non-right-handers inherently more symmetric in function. The underlying genetic program that governs this asymmetrical brain development is the biological reason for the universal bias toward right-handedness.
Defining the Spectrum of Dexterity
Dexterity exists on a continuum, and it is necessary to distinguish between true ambidexterity and other forms of two-handed use. True ambidexterity is defined by equal performance ability with both hands for any given task, meaning the speed and accuracy are near identical. This level of equal competence is extremely uncommon, with prevalence often cited as less than 1% of the population.
A far more common phenomenon is mixed-handedness, also known as cross-dominance, which is frequently confused with true ambidexterity. Mixed-handed individuals exhibit a preference for different hands depending on the specific task. For example, a person might write with their right hand but prefer to throw a ball or use a computer mouse with their left hand.
Mixed-handedness is characterized by an ambiguity in hand preference, not necessarily equal skill, and is estimated to affect up to 9% of the population. To accurately measure true ambidexterity, researchers must use standardized performance tests, such as the alphabet writing test, which measures both the speed and quality of execution with each hand. Handedness is typically determined by preference questionnaires and objective performance metrics.
The distinction between these categories is important, as mixed-handedness has been reported to have a higher prevalence in certain neurodevelopmental conditions. While a person’s preference can be easily assessed, true ambidexterity can only be confirmed by demonstrating similar high-level motor performance in both limbs. The low incidence suggests that a strong lateralization of motor skills is the standard organizational structure of the human brain.
Acquisition and Training
The question of whether ambidexterity can be learned is distinct from congenital ambidexterity. The process of learning a new skill with the non-dominant hand relies on the brain’s capacity for neuroplasticity, which allows neural structures and functions to change in response to experience and repetitive practice. Training the non-dominant hand can certainly lead to a significant increase in its proficiency for specific tasks.
Adult training often focuses on developing fine motor skills, including writing, complex manipulations, and drawing with the non-preferred hand. Practicing a new skill strengthens the corresponding motor brain areas in the contralateral hemisphere, improving coordination and control. Training to write with the left hand, for instance, enhances the function of the motor cortex in the right hemisphere.
Achieving true ambidexterity—equal, high-level competence across all motor tasks—is difficult due to entrenched neurological pathways established over a lifetime. While a person can become ambidextrous for a specific task, such as playing a musical instrument or hitting a ball, full ambidexterity remains unlikely for most people. The benefits of training are specific to the motor skills being practiced and do not generally translate into broad cognitive enhancements.
Some studies suggest that individuals may naturally become more ambidextrous as they age because the dominant hand can lose some of its specialized dexterity. This shift is not an increase in the non-dominant hand’s skill but a decrease in the dominant hand’s superiority, resulting in a narrower performance gap between the two. Training the non-dominant hand is a practical way to develop functional symmetry, but it is a process of acquired skill, not a change in fundamental brain organization.