This paper will closely look at cross dominance in left handed people. Cross dominance may also be referred to as cross laterality or mixed dominance. It is a situation in which an individual prefers areas of dominance that fall on different sides of the body. The concept of handedness is based on which hand becomes the dominant hand and is thus used to perform most tasks.
Other than the hand, other areas of dominance in a person are the foot, ear and eye. Cross dominance is thought to increase in persons whose fine motor skills are on the left hand. This paper looks at both the factors leading to the increase in cross dominance in fine motor skills in left handed people and their implications on the individual. Cross dominance is thought to be both advantageous and disadvantageous.
Cross dominance is the preference (or favor of) that an individual gives to one side of the body or the other. Basing on this preference for one side of the body, an individual can be said to be either right handed or left handed. A left handed person favors the left hand when carrying out most tasks. Some people have equal preference for the left and right side and are referred to as ambidextrous. In a left sided person, the right side of the brain is dominant.
There are four areas in the body where dominance can be expressed. These areas comprise of the hand, the foot, the ear and the eye. All these areas should fall on the same side of the body in an ideal situation. Therefore, in a left handed person all the areas should be on the left side.
If one area of dominance is found on the opposite side, then that area is described as cross dominant relative to the dominant side of the body. For instance, when a left handed person prefers the right foot over the left one the phenomenon is described as cross-hand dominance.
Cross-Dominance in Left Handed People
Fine motor skills are the small actions of the hands, wrists, fingers, feet, toes, lips and the tongue. These actions are necessary for precision when carrying out some tasks. A person who is left handed would ideally have all the fine motor skills on the left side of the body. All the skills would then be controlled from the right cerebral hemisphere. This is called the dominant hemisphere.
Research has shown that cross dominance is more likely to occur in left handed people than right handed people. Several reasons have been put forth to explain this but none of them is really convincing enough. Some researchers believe that naturally left handed children may become cross dominant with regard to the use of the left hand owing to some factors (Treder, 2009).
Right handed individuals make up the majority of the world population. The natural left hander is, therefore, taught from an early age by right handed individuals. The left handed child learns to adapt the use of the right hand from these adults (Maples, 2002). The child will learn to carry out fine motor skills that were initially supposed to be carried out using the left hand.
This kind of cross dominance is common in societies that do not tolerate left handedness. Left handedness in some societies is considered a bad omen. This prompted parents and teachers of naturally left handed children to force them to use the right hand. This scenario results in a situation where the child will prefer to eat or write with the right hand while other tasks like kicking a ball are retained on the left foot.
Another factor that has been implicated for causing cross dominance is the design of tools. Many tools are designed for use by the right handed individuals without accommodation for those with preference for the left side of the body. From an early age a child who naturally prefers the left side of the body meets these challenges. Some notable tools that previously did not have provision for left sidedness in their designs include scissors, riffles and circular saws.
The scissors for instance do not cut if operated using the left hand. As children meet these challenges early in life, they learn to adapt to the use of their right side of the body like the hands to operate these tools. This form of mixed laterality is therefore an adaptive response to ones environment. Adaptation to the environment is necessary for the continued survival of man on earth.
Efficiency and the task to be performed may also cause cross laterality. The efficiency achieved when performing a task may encourage an individual to adapt the use of a hand or side of the body that they achieve greater efficiency with ease. Some tasks like knitting may also encourage mixed laterality.
Fine motor skills are controlled on the contra-lateral cerebral hemisphere. A left handed individual’s fine motor skills are controlled from the right cerebral hemisphere (Stanley, 1990). The cerebral hemisphere codes for muscles that control these skills. It is thought that in left handed people there may be a shift in these coding. There may be some events during embryological development that lead to left sidedness. These events could also result in the development of cross laterality.
In one study it was found that a fetus exposed to excess testosterone in utero developed cross dominance after birth (Reinisch, 1992). During brain development, if the right cerebral hemisphere is exposed to excess testosterone, then the left hemisphere develops faster. This mismatch in growth gives room for cross laterality. In some left handed people there is a considerable amount of malleability of their brains.
Their brains permit the existence of dominant areas of the body on opposite side of the brain. It is not understood why this happens more often in left handed people than in right handed persons. A rather controversial theory has been suggested to explain this. It is thought by some researches that this phenomenon is as a result of a brain abnormality that occurs either during brain embryogenesis or at birth.
Conclusion
Cross dominance is a phenomenon that affects both the right handed persons and the left handed people. If a person is left handed in fine motor skills, the ability to have cross dominance is increased. The increase can be attributed to number of factors some of which are socio-cultural.
Some factors that are linked to brain development are controversial and require more research in order for them to be more accepted. Cross dominance is thought to confer both advantages and disadvantages. It makes the performance of some motor skills clumsy. It is known to give athletes an upper hand in some sports like gymnastics.
References
Maples, W. (2002). Eyedness, Hand-Eye Dominance and Academic Performance. Web.
Reinisch, M., & Sanders, A. (1992). Effects of prenatal exposure to diethylstilbestrol (DES) on hemispheric laterality and spatial ability in human males. Horm Behav, 26 (1), 62–75.
Stanley, C. (1990). Left-handedness: behavioral implications and anomalies. Web.
Treder, S. (2009). Article on the Advantage of Cross Dominance in Baseball Including Statistics. The Hardball Times. Web.