Laterality
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Laterality refers to the preference that most humans show for one side of their body over the other. It may also apply to animals.
The significant majority of humans are right-handed. Many are also right-sided in general (that is, they prefer to use their right eye, right foot and right ear if forced to make a choice between the two). The reasons for this are not fully understood, but it is thought that because the left cerebral hemisphere of the brain (which is dominant over the right cerebral hemisphere in most humans) controls the right side of the body, the right side is generally stronger.
Human cultures are predominantly right-handed, and so 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". Also, sinistra, the Latin word from which the English word "sinister" was derived, means "left".
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.
Ambidexterity is when a person has approximately equal strength in 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. However, this preference is not necessarily consistent for all activities. Some people may for example use their right hand for writing, and their left hand for playing racket sports and eating.
Also, it is not uncommon that people preferring to use the right hand prefer to use the left leg, e.g. when using a shovel. In many cases, this may be because they are disposed for left-handedness but have been trained for right-handedness. Shovels are usually designed to be used with either foot.