Talent and Deficit in Left-Handedness
Howard I. Kushner
Approximately 10 percent of the human population is left-handed and probably has been since the beginning of our species. For most of human history, including much of the planet today, left-handedness has been stigmatized. Thus, the words “left” and “left-hand” in almost all the world’s languages have negative connotations—from “sinister” in Latin and Italian to “dishonest” in Mandarin. Despite the fact that males are more likely to be left-handed, left-handedness has been gendered female in most cultures. These prejudices are reflected and reinforced in practices aimed at restricting the use of the left hand to the most disdained, but necessary, human tasks such as cleaning oneself after elimination of waste.
Yet for all the attention left-handedness has received, almost every basic question about its origin, extent, function, and consequences remains unanswered. Although numerous observers have attempted to uncover the cause of left-handedness, so far none have been able to solve the mystery.
Part of the reason for this failure is that the causes and consequences of left-handedness have been examined and interpreted within the confines of distinct disciplinary perspectives of science/medicine and the humanities. Though examining similar issues, humanists and scientists rarely interact or even seem aware of each other’s existence. This divide is most apparent between those who have approached the problem of left-handedness from the perspective of (neuro)psychology and those who have examined it in the context of the history and culture.
Solving the mysteries of handedness, however, may require bringing humanities into conversation with the sciences and medicine. Because individual researchers generally do not possess the training or knowledge to cross disciplinary boundaries, collaborations are particularly useful. Although in science and medicine such collaborations are normal, they are less often encouraged in the humanities, and, in any case, rarely will humanists be included in scientific investigations. Indeed, external funding protocols often exclude humanists. Crossing the science/humanities divide is difficult, but its rewards, at least in handedness research, can be substantial, as I illustrate below. I begin with the findings of science and medicine and then place them in historical and cultural context.
In 1903, the influential Italian criminologist Cesare Lombroso claimed that left-handedness was connected with feeble-mindedness, mental illness, and criminality. Lombroso’s views, repackaged to fit with contemporary scientific discourses, have had great resilience. The connection between left-handedness and illness gained renewed legitimacy in the 1980s with Harvard University neurologist Norman Geschwind’s studies connecting left-handedness with an array of disorders, including autoimmune diseases, psychiatric disorders, mental retardation, and learning disabilities. Following Geschwind, a number of studies claimed that left-handedness was either the cause or result of disorders such as schizophrenia, autism, attention deficit disorders, dyslexia, stuttering, and Tourette syndrome. These associations continue to be debated in current studies. If this connection is robust, left-handedness may be one of the greatest threats to the mental health of our planet’s population.
Like so many other human behaviors, the explanations for handedness have been divided between notions that it is learned versus inherited. By the late twentieth century, a consensus had emerged that handedness was best understood from a genetic perspective. Investigations ever since have focused on which genetic model best explains the incidence of left-handedness.
Given the combination of stigmatization and the putative relationship between left-handedness and learning disorders, why are there any left-handers at all? This question has led a number of researchers to assume that there must be a selective advantage to left-handedness. They point to persistent reports that left-handers display greater creativity and intellectual prowess than right-handers. So is left-handedness a deficit or an enhancer of creativity—or both?
Since the mid-nineteenth century, most researchers have assumed that left-handers are right-brained in terms of both motor and language function. That is, they have believed that given the contralateral nature of brain/side function—that the right side of the body is controlled by the left cerebral hemisphere and vice versa—left-handers would be right-brained for language. This is not so. Imaging studies reveal that only 18 percent of left-handers are localized to the right hemisphere for language and speech, while 12 percent are bilateral, having language in both hemispheres. Thus, for 70 percent, language and speech are located in the left hemisphere. Complicating matters, 5 percent of right-handers also have right-hemisphere language dominance, with 95 percent being left-hemisphere dominant.
This anomaly—that the majority of left-handers are left-brained for language and only 18 percent of left-handers are right-brained localized—must be taken into account in reexamining the claims that left-handers are at greater risk for learning disabilities than right-handers. Although the classification and etiology of learning disorders themselves remain contested, there is general agreement that autisms, attention deficit disorders, schizophrenias, and dyslexias are neurological conditions that are intimately tied to language. While it is true that other disabilities, especially Tourette syndrome and stuttering, involve motor functions as well as speech and language, they too are understood and treated as neuropsychiatric conditions that at bottom are the result of cerebral malfunctions. The claims that left-handers also have an increased probability of being talented and creative are related to brain function.
Although the associations between handedness and learning disorders and talent lately have been viewed in a neurobiological frame, placing them in historical and cultural context provides a deeper understanding of the relationship between learning disorders and handedness. In 1909 the French anthropologist Robert Hertz insisted that whatever its biological substrate, the predominance of right-handedness ultimately was a cultural artifact driven by a primitive human urge to divide the world into binary oppositions in which the right was viewed as sacred and the left as profane. Influenced by the popular early twentieth-century British ambidextrous culture society, Hertz argued that ending discrimination against left-handedness would unleash the power of both hands and, thus, both cerebral hemispheres. The results, he insisted, would allow repressed talents and creativity to flourish. Hertz’s study and methods have influenced subsequent generations of cultural anthropologists and historians of handedness.
Among Hertz’s most enduring contributions, writes Chris McManus, one of the few neuroscientists who include historical and cultural contexts in his research, was Hertz’s confrontation with the age-old debate of whether the etiology of handedness was biological or cultural. Although, McManus writes, Hertz conceded that “the right is sacred because it is the stronger and more skillful . . . that did not mean the symbolism is merely biological.” Rather, Hertz demonstrated that “it is only the social system of which we are a part, with its dualistic views on almost everything, that provides the power and energy to transform the right to the sacred and left to profane.”
The work of Hertz and the cultural anthropologists and historians who followed him suggests that attempts to identify the risk for learning disorders based on hand preference alone probably cannot tell us what we need to know about the etiology of learning disorders or, for that matter, of the causes of creativity and talent. Historical and cultural discrimination against left-handers has played an important role in the identification and perhaps even in the etiology of some learning disorders. For instance, many twentieth-century British and American educators, psychologists, and psychiatrists advocated forcing left-handed children to write with their right hands. These experts asserted that a child’s decision to rely on his or her left hand was a reflection of a defiant personality that could best be corrected by forcible switching. The methods used to “retrain” left-handers were often tortuous, including restraining a resistant child’s left hand.
In contrast, those who saw left-handedness as inherited but natural not only disapproved of forced switching, but also often warned of its putative negative consequences, especially stuttering. These claims were given credence in the 1930s and 1940s by University of Iowa researchers and their students who published detailed case studies of patients whose stuttering was cured by switching them back to their original dominant hand. Despite robust statistical and clinical evidence, the connection between forced hand switching and stuttering has largely been forgotten. Similar to the Iowa researchers, recent imaging studies have suggested that stuttering is tied to disturbed signal transmission between the hemispheres.
Finding answers to the most interesting questions about the connections between disabilities and handedness will require a biologically informed historical and cultural approach. My current book project, tentatively titled “Talent and Deficit, the Anomaly of Left-Handedness,” examines these controversies in an attempt not only to explore the mysteries of left handedness, but also to call on historical methods to help identify clues that will aid us in identifying the cultural impact, if any, of handedness on human disease, health, cognition, and behavior.
Geschwind, N., & Behan, P. 1982. “Left-Handedness: Association with Immune Disease, Migraine, and Developmental Learning disorder.” Proceedings of the National Academy of Sciences 79(16).
Hopkins, W. D., Phillips, K. A., Bania, A., Calcutt, S. E., Gardner, M., Russell, J., et al. 2011.”Hand Preferences for Coordinated Bimanual Actions in 777 Great Apes: Implications for the Evolution of Handedness in Hominins.” The Journal of Human Evolution, 60(5).
Kushner, H. I. 2011.”Cesare Lombroso and the Pathology of Left-Handedness.” The Lancet, 377(9760).
Kushner, H. I. 2011. “Retraining the King’s Left Hand.” The Lancet, 377(9782).
Kushner, H. I. 2011. “Retraining Left-Handers and the Aetiology of Stuttering: The Rise and Fall of an Intriguing Theory.” Laterality, Epub ahead of print: http://www.ncbi.nlm.nih.gov/pubmed/22332811
Lindell, A. K. 2011. “Lateral Thinkers Are Not so Laterally Minded: Hemispheric Asymmetry, Interaction, and Creativity.” Laterality, 16(4).
McManus, I. C. 2002. Right Hand, Left Hand: The Origins of Asymmetry in Brains, Bodies, Atoms, and Cultures. London: Weidenfeld & Nicolson.