Left-handedness (left lateral)

Left-handedness is the preference for using primarily the left hand to perform everyday activities, such as writing, eating, or throwing an object. Left handedness is less common than right handedness and has been linked to certain neuropsychiatric traits such as schizophrenia and bipolar disorder.

Left-handed people have a definite preference for using the left hand over the right, and this can be seen from early stages of development, even in utero, when the embryo begins to move only one arm. Constant use of one hand throughout life can cause changes in bone and bone density. In addition, it has been observed that left laterality is related to language lateralization in the brain, that is, the side that plays a major role in language. Its connection with some neuropsychiatric traits, such as schizophrenia and bipolar disorder, has also been investigated.

Genetic influence may play a crucial role in explaining the differences in language processing, spatial skills and emotions between left- and right-handers. However, the exact etiology of this trait is not yet fully understood, although it has been shown to be highly polygenic. In addition to genetic influence, left laterality can also be explained by environmental factors that could affect from prenatal stages. However, the precise effects of such environmental factors are not yet fully known.

The worldwide prevalence of left-handedness is about 10%, and it is also higher in males than in females. The problem with the study of left-handedness is that non-right-handed people have historically been forced to use their right hand for everyday tasks, which has led to some left-handed or ambidextrous people becoming right-handed due to this imposition. This has caused the rate of forced right-handedness to vary between cultures and, although it has decreased in recent decades, it may have affected the accuracy of left-handed prevalence statistics.