The human brain’s specialization often leads to a preference for one side of the body over the other in tasks like writing or kicking, a concept known as dominance. When this pattern isn’t consistent across all activities, it’s termed cross-dominance. An intriguing question is whether this variation influences cognitive abilities or intelligence.
Understanding Cross Dominance
Cross-dominance, also known as mixed-handedness or mixed laterality, describes a natural variation where an individual exhibits a blend of dominant sides for different bodily functions. For instance, someone might write with their right hand but prefer their left eye for tasks like aiming. Another example is a person who is left-handed for writing but uses their right foot to kick a ball. Individuals can also switch dominance depending on the specific task, such as writing with the right hand but eating with the left.
Brain Lateralization and Dominance
The neurological foundation for these preferences lies in brain lateralization, which refers to the specialization of the two cerebral hemispheres for different functions. Each hemisphere tends to process sensory input and control motor skills for the opposite side of the body. For example, the left hemisphere generally controls the right side of the body, and the right hemisphere controls the left side.
This specialization extends to cognitive functions. For most people, approximately 90% of individuals are right-handed, and about 95% of these right-handers have language functions primarily located in their left hemisphere. In left-handed individuals, this pattern is more varied, with around 70% still showing left-hemisphere language dominance, while others may have language functions in the right hemisphere or distributed across both. While certain functions are often lateralized, the brain remains highly interconnected, with both hemispheres working in concert through the corpus callosum to facilitate complex actions and thoughts.
The relationship between handedness and language dominance is a natural phenomenon, with the incidence of right-hemisphere language dominance increasing with the degree of left-handedness. This suggests a spectrum rather than a rigid division in how functions are distributed across the brain’s hemispheres.
Exploring the Connection to Intelligence
The question of whether cross-dominance correlates with intelligence has been a subject of popular interest and scientific inquiry. Historically, anecdotes and theories suggested a link, with some famous cross-dominant individuals perceived as highly intelligent or creative. Some theories propose that mixed dominance might lead to increased communication between the brain’s hemispheres, potentially fostering unique creative or problem-solving abilities.
Despite these popular notions, scientific consensus, based on extensive research, indicates no direct or significant link between cross-dominance and overall general intelligence. A systematic review and meta-analysis of studies published since 1900, involving over 3,500 children aged 5 to 12, concluded there is no reliable association between crossed laterality and either academic achievement or intelligence. While some studies might identify minor correlations in specific cognitive tasks, these findings are often inconclusive and do not signify a broader impact on general intelligence.
Intelligence is a multifaceted construct influenced by a wide array of genetic, environmental, and developmental factors, far beyond simple patterns of handedness or laterality. The brain’s adaptability and interconnectedness allow for diverse organizational patterns without necessarily conferring an advantage or disadvantage in overall cognitive capacity. Therefore, while cross-dominance represents an interesting variation in human neurological organization, current scientific evidence does not support the idea that it directly predicts higher or lower intelligence.