Published 16 December 2008, doi:10.1136/bmj.a2906
Cite this as: BMJ 2008;337:a2906

Editorials

Christmas 2008

Left-right discrimination in medicine

Are left handed people the last great neglected minority?

Right and left are so very confusing. Perceptually, distinguishing right and left is surprisingly difficult, as Gormley and colleagues’ linked article shows (doi:10.1136/bmj.a2826).¹ Scientifically the origins of a brain polymorphism that makes 90% of people use their right hand for skilled activities but the other 10% use their left hand are unclear.² And socially, ethically, and educationally, there is confusion over the needs and rights of those people whom I sometimes describe as the last great neglected minority—left handers.

Right handedness is so obvious a fact of life that few people realise how unusual it is. All other species, except perhaps chimpanzees,³ are made up half and half of right handers and left handers. Nor is it coincidence that humans alone have language, and that language is mostly located in the left hemisphere, which controls the right hand. The left hemisphere processes information more quickly than the right hemisphere. This speed is required both for online processing of grammar and the rapid movements needed in speech and fine motor skills.

It is less surprising that left and right are confused than that they can be distinguished at all, and that ability also seems to be unique to humans.⁴ The physicist Ernst Mach showed that true right-left discrimination, the association of arbitrary stimuli to right or left sides, requires a system that is itself asymmetric. Because men’s brains are somewhat more asymmetric than women’s brains, and right handed people’s brains are more asymmetric than left handed people’s brains, right-left confusion is more prevalent in women and left-handed people.²

Right-left discrimination is learnt surprisingly late in life. The core problem is that, when facing me, your right hand is actually on my left side. This provides immense scope for disastrous confusion in surgery. Fortunately, marking the operation side with a permanent felt tip marker when the patient is fully conscious provides a ready solution. Interpreting radiographs and brain scans, with their opposite left-right conventions, is another matter, so the words "right" and "left" need to be readily visible on all images (this is especially important for images from the 1/10 000 patients with situs inversus).

The technological world in which we live was designed and built mainly by right handed people, with little heed of the needs of left handers. The result is that, despite a 10th of people being left handed, digital cameras with buttons on the left seem non-existent. Although health and safety regulations are often invoked for seemingly trivial reasons, the needs of left handers remain mostly ignored, so that when a badly designed electric saw cuts off the fingers of a left handed person, the person is likely to be blamed rather than the design of the equipment. Most complex equipment in medicine is also designed mainly for right handed people (although it is said, albeit with some dissent,⁵ that Boyle’s anaesthetic machine was better suited for left handed people because Boyle himself was left handed⁶).

Ancient commentators emphasised the need for surgeons to be skilled with both hands. The Roman physician Celsus said that surgeons should be "ready to use the left hand as well as the right," which echoed the ideas of Hippocrates, who said surgeons should, "Practise all the operations . . . with each hand . . . to attain ability, grace, speed, painlessness, elegance and readiness." Of course this is a counsel of perfection—most people have one hand that limps along without the eloquent movements of the other. However dextrous and practised, most surgeons are probably little different, although the exigencies of living in a right handed world probably mean that left handed surgeons are a little more bilateral than their right handed colleagues.

Few surgeons work alone—they have assistants who mop, swab, suck, cut, and hand them instruments when needed. The 19th century surgeon, Sir Benjamin Brodie, recognised the problem when he wrote, "How much inconvenience would arise were it necessary for different individuals to co-operate in manual operations, if some were to use one hand and some the other?"⁷ It is a good point because left handed people may be disadvantaged when collaborating. Despite one study suggesting a scarcity of left handed surgeons,⁸ Lieske’s linked article (doi:10.1136/bmj.a2883)⁹ and my own data¹⁰ indicate that left handed surgeons are as prevalent as in the general population. Of course, as Lieske notes, left handed surgeons (and left handed endoscopists and radiologists¹¹) may still have problems—for example, left handed instruments not being available or needles being mounted the wrong way round (even if asymmetric abdominal anatomy and the mechanics of laparoscopes do sometimes work in left handed people’s favour). Whether the handedness of surgeons really matters—for surgeon, patient, or hospital—should be easy to discover. To be left in confusion surely isn’t right.

Cite this as: BMJ 2008;337:a2906

¹ University College London, London WC1E 6BT

Research, doi:10.1136/bmj.a2826; doi:10.1136/bmj.a2883

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Competing interests. I am a right hander, the son of a left hander, the father of a left hander, and the onlie begetter of Right Hand, Left Hand. If this editorial encouraged anyone to buy this book I would also have a financial interest, albeit pretty small.

Provenance and peer review: Commissioned; not externally peer reviewed.

References

1. Gormley GJ, Dempster M, Best R. Right-left discrimination among medical students: questionnaire and psychometric study. BMJ 2008;337:a2906.[Free Full Text]
2. McManus IC. Right hand, left hand: the origins of asymmetry in brains, bodies, atoms and cultures. London: Weidenfeld and Nicolson, 2002.
3. Hopkins WD. Comparative and familial analysis of handedness in great apes. Psychol Bull 2006;132:538-59.[CrossRef][Web of Science][Medline]
4. Corballis MC, Beale IL. The psychology of left and right. Hillsdale, NJ: Lawrence Erlbaum Associates, 1976.
5. Padfield A. Henry Edmund Gaskin Boyle OBE (1875-1941)—originator of the eponymous machine. Anaesth News 2006;231:28-9.
6. Maltby JR. Notable names in anaesthesia. London: Royal Society of Medicine, 2002.
7. Brodie BC. Psychological inquiries. 4th ed. London: Longman, Green, Longman, Roberts and Green, 1862.
8. Schott J, Puttick M. Handedness among surgeons [letter]. BMJ 1995;310:739.[Free Full Text]
9. Lieske B. "I don’t know what you’re doing, it looks all wrong to me"—the left handed surgical trainee. BMJ 2008;337:a2883.[Free Full Text]
10. McManus IC, Hallgeir J. Right and left-handedness and medical speciality choice in a large prospective study of medical students and doctors. 2008. www.ucl.ac.uk/medical-education/publications/unpublished-manuscripts/Handedness_and_Medical_Specialities.
11. Dosani S. Sinister choices. BMJ Careers 2007:108. http://careers.bmj.com/careers/advice/view-article.html?id=2619.

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