The term laterality refers to asymmetric preference, usage, skill, or specialization of symmetric body parts in an organism. Humans exhibit laterality in many ways, including limb dominance such as left and right handedness and footedness as well as specialization of one brain hemisphere over the other for certain functions such as language. Many other animals have also been shown to exhibit laterality in their own ways.
Laterality in humans The majority of humans are right handed and prefer to use the right side of their body in general (right foot, eye, and ear, for example), although this is not the case for everyone. Some prefer to use their left side, have no preference, or have mixed preferences. Ambidexterity is when a person has approximately equal skill with both hands and/or both sides of the body. True ambidexterity is very rare. Although a small number of people can write competently with both hands and use both sides of their body well, even these people usually show preference for one side of their body over the other. Which side a person prefers to use is not necessarily consistent across all parts of the body. For example, it is not uncommon for a typically right handed person to prefer to use their left leg, e.g. when using a shovel, kicking a ball, or operating control pedals. Approximate statistics, complied in 1981, are given below:
Favoring right hand: 88.2% Favoring right foot: 81.0% Favoring right eye: 71.1% Favoring right ear: 59.1% Same hand and foot: 84% Same ear and eye: 61.8% Lateral preference also is not always consistent across different activities performed by the same part of the body. Some people may, for instance, use their right hand for writing, and their left hand for playing racket sports and eating. In the sport of cricket, some players may find that they are more comfortable bowling with their left or right hand, but batting with the other hand. This inconsistent preference is referred to as cross dominance.
Different expressions Board footedness The stance in a boardsport is not necessarily the same as the normal-footedness of the person. In skateboarding and other board sports, a "goofy footed" stance is one with the right foot leading. A stance with the left foot forward is called "regular" or "normal" stance. Jump and spin Direction of rotation in figure skating jumps and spins is not necessarily the same as the footedness or the handedness of each person. A skater can jump and spin counter-clockwise (the most common direction), yet be left-footed and left-handed. Ocular dominance The eye preferred when binocular vision is not possible, as through a keyhole or monocular microscope.
Laterality in Human Society Since human cultures are predominantly right-handed, the right-sided trend may be socially as well as biologically enforced. This is quite apparent from a quick survey of languages. The English word left comes from the Anglo-Saxon word lyft, which means 'weak' or 'useless'. Similarly, the French word for left, gauche, is also used to mean 'awkward' or 'tactless', and sinistra, the Latin word from which the English word sinister was derived, means 'left'. Similarly, in many cultures the word for right also means 'correct'. The English word right comes from the Anglo-Saxon word riht, which also means 'straight' or 'correct'. This linguistic and social bias is not restricted to European cultures: for example, Chinese characters are designed for right-handers to write, and no significant left-handed culture has ever been found in the world. The social bias against left handedness can lead to people who would naturally prefer their left hand being forced or pressured into using their right hand instead. When a person is forced to use the hand opposite of the hand that they would naturally use, this is known as forced laterality, or more specifically forced dextrality. A study done by the Department of Neurology at Keele University, North Staffordshire Royal Infirmary suggests that forced dextrality may be part of the reason that the percentage of left-handed people decreases with the higher age groups, both because the effects of pressures toward right-handedness are cumulative over time (hence increasing with age for any given person subjected to them) and because the prevalence of such pressure is decreasing, such that fewer members of younger generations face any such pressure to begin with. It also has been suggested that in many cases, cross dominance may occur because a person is disposed for left-handedness but has been trained for right-handedness, which is usually attached to learning and behavioral disorders.
Speech and Laterality in the Brain
… excerpt ends here. Continue reading the full article.
