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Fiction: The science in Sherlock Holmes

Nature volume 549, pages 332333 (21 September 2017) | Download Citation

Maria Konnikova detects the fictional sleuth's inner researcher, 130 years on from his 'birth'.

Sherlock Holmes applies his chemical skills in this 1893 illustration by Sidney Paget. Image: AF Fotografie/Alamy

When Sherlock Holmes first meets Dr John Watson, he identifies the physician's background at a glance. To many, that moment in Arthur Conan Doyle's A Study in Scarlet (1887) — Holmes's debut — is a smile-worthy flight of fancy. Except it isn't entirely fantastical. One of Conan Doyle's mentors at the University of Edinburgh, UK, where he trained as an ophthalmologist, was the surgeon Joseph Bell. And it's to him that we owe the famed exchange about Afghanistan, as well as much of Holmes's character.

Bell's accuracy in diagnosis is well documented, and was so renowned that he served as Queen Victoria's personal surgeon when she visited Scotland. Central to this ability were his powers of observation. It was while working as Bell's ward assistant that Conan Doyle witnessed the doctor correctly identifying the former profession of a retired army officer, as well as where he had served — Barbados. “The student must be taught to observe,” Bell asserted. A patient would believe in the doctor's curative prowess “if he sees that you, at a glance, know much of his past”. It was a message that burrowed into the young Conan Doyle's mind. As he wrote to Bell years later, “Round the centre of deduction and inference and observation which I have heard you inculcate, I have tried to build up a man who pushed the thing as far as it would go — further occasionally.”

Renaissance man

Holmes, of course, is more than a diagnostician. He is a chemist, psychologist, logician, inventor: all faces that filled Conan Doyle's pre-Holmesian life. In that era of profound scientific change, apparently improbable ideas — such as evolution and the existence of electromagnetic waves — were suddenly central to the conversation. Having rejected his early Jesuit education for Darwinism and empiricism, Conan Doyle himself was close to the ongoing revolution.

At Edinburgh, he encountered many of the thinkers at the forefront of innovation. The surgeon and pioneer of antiseptic medicine Joseph Lister exposed him to Louis Pasteur's work on germ theory. Conan Doyle became fascinated with the possibilities opening to medicine — a fascination that Holmes would take to fictional heights. In A Study in Scarlet, for instance, Holmes exclaims, “I have found a reagent which is precipitated by haemoglobin, and by nothing else.” The fiction predated the science: German bacteriologist Paul Uhlenhuth discovered the precipitin test for human blood only in 1900.

Surgeon Joseph Bell's acute powers of observation proved an inspiration for Arthur Conan Doyle. Image: Oliphant, Anderson and Ferrier/Wellcome Library, London; CC by 4.0

Conan Doyle also encountered the analytical toxicologist Robert Christison, an expert witness in numerous criminal cases — and an inspiration for Holmes's expertise in poisons. It may have been through his interest in forensic science that Conan Doyle was exposed to another innovator: Alphonse Bertillon, a pioneer of anthropometrics, in which personal measurement is used to identify criminals (fingerprinting owes its existence to his work). Wherever the exposure happened, it stuck. In The Hound of the Baskervilles (1902), we learn that Holmes was considered only the “second highest expert in Europe” on anthropometrics, after Bertillon. (Holmes begs to differ.) Medical training, Conan Doyle believed, fostered a “healthy scepticism” and reliance on facts: the “finest foundations for all thought”. Certainly, Holmes is the greatest of healthy sceptics.

Intentionally or not, Holmes also emerged as a scientific ambassador to the masses. Conan Doyle references Lister's use of carbolic acid for antisepsis in the 1892 story 'The Adventure of the Engineer's Thumb', when Watson uses it while dressing a wound. Before Sigmund Freud became a household name, Holmes was homing in on hidden desires and impulses, although he based his conclusions on decidedly more objective criteria. He muses, for instance, on what would drive a trainer to harm his own horse, a key insight in the 1892 'Silver Blaze'. (Conan Doyle had read Freud's early writings, as well as his 1884 paper 'Über coca', which touted the benefits of Holmes's drug of choice, cocaine.)

Holmes's head

“Holmes is the greatest of healthy sceptics.”

It is perhaps as psychologist that Holmes's contribution to popular science is most evident. Take George Miller's 1956 paper 'The magical number seven, plus or minus two', which posits that humans can cognitively process only around seven pieces of information at any time. It seems to me no coincidence that Miller used an image of a cutaway head with an attic instead of a brain — a probable echo of Holmes's conceptualization of memory in A Study in Scarlet. The brain is originally, Holmes says, like “a little empty attic” but because it lacks “elastic walls”, the “skilful workman is very careful indeed” about what he takes into it.

Holmes's espousal of mindfulness came more than a century before the concept became ubiquitous. Consider his approach to solving a crime: contemplate first, eyes closed, fingers cradled. A passage in the 1891 story 'The Red-Headed League' is a key example. As Watson asks Holmes's opinion of the case, Holmes intones: “It is quite a three-pipe problem, and I beg you won't speak to me for fifty minutes.” What is this but directed meditation? Holmes takes contemplation to a new level, with unilateral focus and no distractions. We even learn that the detective studied with the “head Llama” in Tibet during the Great Hiatus, the period after his supposed murder by Professor Moriarty — another scientist, possibly based on the brilliant but spiteful astronomer Simon Newcomb.

Equally telling is Holmes's detailed exploration of biased decision-making and the clash between cool-headed choices and hot emotion. As he explains to Watson in The Sign of Four (1890), “A client is to me a mere unit, a factor in a problem. The emotional qualities are antagonistic to clear reasoning”, adding that “the most repellent man of my acquaintance is a philanthropist who has spent nearly a quarter of a million upon the London poor”. Emotion is responsible for many of the biases in decision-making explored by psychologists such as Daniel Kahneman, in his Thinking, Fast and Slow (Farrar, Straus and Giroux, 2011).

Holmes is a continually reinterpreted cultural icon. Conan Doyle's 1892 short-story collection The Adventures of Sherlock Holmes alone has sold in the tens of millions. We cannot get enough of him — and that, I think, is a good thing. As a champion of observation and a personification of rationality, Holmes seems more relevant than ever in a world marked by science denialism and over-emotionality. “You know my methods. Apply them,” the detective tells Watson in The Sign of Four. It's high time we did just that.

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  1. Maria Konnikova is the author of The Confidence Game and Mastermind: How To Think Like Sherlock Holmes. Her next book, The Biggest Bluff, explores the balance of skill and chance through a year-long immersion in the world of high-stakes poker. She is a contributing writer for The New Yorker and host of podcast 'The Grift'.

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Correspondence to Maria Konnikova.

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