Left-handedness, or sinistrality, is the preference for using the left hand over the right hand for activities such as writing and throwing. It is estimated that approximately 10% of the world’s population is left-handed (Heilman et al., 1999). Despite the prevalence of left-handedness, its causes are not yet fully understood.

Theories about the causes of left-handedness range from genetic factors to environmental influences. For example, some researchers hypothesize that handedness is the result of a combination of genetic and environmental factors (Geschwind & Galaburda, 1987). Other theories suggest that handedness is determined by hormones during pregnancy (Deoni, 2014).

Research has also suggested that left-handedness may be associated with certain cognitive abilities. In a study of 949 participants, Heilman et al. (1999) found that left-handed people tend to outperform right-handed people in tasks involving visuospatial abilities such as mental rotation and visual perception. In addition, left-handedness has been linked to higher levels of creativity (Geschwind & Galaburda, 1987).

Left-handedness has also been connected with other physical and mental health conditions. Studies have found that left-handed people are more likely to suffer from insomnia and migraine headaches (Coren, 1999). Left-handedness has also been linked to higher rates of some mental health conditions, such as schizophrenia and bipolar disorder (Coren, 1999).

Despite the various theories and research findings related to left-handedness, there is still much to be learned about its causes and its links to different cognitive and physical abilities and health conditions. Future studies could focus on investigating the relationship between left-handedness and various health conditions, as well as exploring the genetic and environmental factors that are associated with it.


Coren, S. (1999). The Left-Hander Syndrome: The Causes and Consequences of Left-Handedness. New York: Free Press.

Deoni, S. (2014). Prenatal Development and Laterality: Implications for Understanding the Neurobiology of Handedness. Annals of the New York Academy of Sciences, 1320(1), 13-25.

Geschwind, N., & Galaburda, A.M. (1987). Cerebral Lateralization: Biological Mechanisms, Associations, and Pathology. Cambridge, MA: MIT Press.

Heilman, K.M., Nadeau, S.E., Beversdorf, D.Q., & Watson, R.T. (1999). Hand preference and visuospatial ability: Implications for the mechanisms underlying cerebral lateralization. Neuropsychology, 13(3), 420-430.

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