Since his first appearance in 1887, Sherlock Holmes has become an industry — the Guinness Book of World Records notches him as the most-played movie character in history, with some 200 actors playing the role — and a metaphor for clear thinking.
Psychologist Maria Konnikova’s “Mastermind: How To Think Like Sherlock Holmes” unpacks the Holmesian method of inquiry in the language of cognitive science.
From her research, we’ll take a look at how anyone can observe and deduce like the fictional detective.
When Holmes first met Dr. Watson, his soon to be partner in solving crimes, the detective made a certain and offhand claim: 'You have been in Afghanistan, I perceive.'
Watson's reply: 'How on Earth did you know that?'
Holmes, naturally, deduced it:
'I knew you came from Afghanistan...
The train of reasoning ran, 'Here is a gentleman of a medical type, but with the air of a military man. Clearly an army doctor, then. He has just come from the tropics, for his face is dark, and this is not the natural tint of his skin, for his wrists are fair. He has undergone hardship and sickness, as his haggard face says clearly. His left arm has been injured. He holds it in a stiff and unnatural manner. Where in the tropics could an English army doctor have seen much hardship and got his arm wounded? Clearly in Afghanistan.''
That is deep-level observation, Konnikova says. Holmes sees his new acquaintance's symptoms of tropics, sickness, and injury, and is able to see how they fit together -- deducing his personal history from his appearance.
When Holmes famously quips that the solution of a case is 'elementary,' he's not simply dismissing the detective work as easy. Rather, he's talking about elements, the essentials of a situation.
'Before turning to those moral and mental aspects of the matter which present the greatest difficulties, let the enquirer begin by mastering more elementary problems.'
As a physicist begins with the laws relevant to a problem, a detective begins with the facts of a case before adding in interpretation.
'Whatever the specific issue, you must define and formulate it in your mind as specifically as possible -- and then you must fill it in with past experience and present observation,' Konnikova writes. 'As Holmes admonishes Lestrate and Gregson when the two detectives fail to note a similarity between the murder being investigated and an earlier case, 'There is nothing new under the sun. It has all been done before.''
When Holmes is listening to -- or perceiving -- somebody, he's not fussing with his iPhone.
'Holmes ... focuses all of his faculties on the subject of observation ... He listens, as is his habit, 'with closed eyes and fingertips together.' ... He will not be distracted by any other task. As passive observers, we are not doing anything else; we are focused on observing.'
Listening, we have learned, isn't just a matter of hearing the words people say. Instead, we need to attend the whole of a person's expression to get all the nonverbal information that's being communicated -- but so easy to ignore.
When Holmes is dealing with a particularly thorny case, he occupies himself with another activity, like playing the violin or smoking a pipe.
The thorniest of cases are 'three pipe problems.'
From 'The Red-Headed League':
''To smoke,' (Holmes) answered. 'It is quite a three pipe problem, and I beg that you won't speak to me for fifty minutes.' He curled himself up in his chair, with his thin knees drawn up to his hawk-like nose, and there he sat with his eyes closed and his black clay pipe thrusting out like the bill of some strange bird. I had come to the conclusion that he had dropped asleep, and indeed was nodding myself, when he suddenly sprang out of his chair with the gesture of a man who has made up his mind and put his pipe down upon the mantelpiece.'
Citing psych research, Konnikova contends that the pipe smoking is a way for Holmes to constructively distract himself from his thinking. In the same way that playing the violin helps the detective to sort through his thoughts, packing and smoking his pipe does his solution-finding imagination a favour by doing something with his body.
For similar reasons, we get ideas on walks.
Holmes is not a one-size-fits-all sort of sleuth, Konnikova says. He tailors his approach to fit the case in question.
When Holmes meets a would-be source of information, he profiles him or her, looking for any advantage that might be communicated by their appearance.
He tells Watson how he nabbed details from a gambling type from intentionally losing a bet to him:
'When you see a man with whiskers of that cut and the 'Pink 'un' (a British football newspaper) protruding out of his pocket, you can always draw him by a bet ... I daresay that if I had put £100 down in front of him, that man would not have given me such complete information as was drawn from him by the idea that he was doing me on a wager.'
Holmes, ever the deducer, reads people's habits from their appearance, a skill all of us can learn.
Holmes knew how to prevent the mid-afternoon dip: not to lose his energy to digestion.
Here's what he said when Watson begged him to eat:
'The faculties become refined when you starve them ... surely, my dear Watson, you must admit that what your digestion gains in the way of blood supply is so much lost to the brain. I am a brain, Watson. The rest of me is a mere appendix. Therefore, it is the brain I must consider.'
For Konnikova, this evidence of Holmes' awareness that your cognitive abilities draw from a finite supply of energy, one that must, if you are to sleuth well, be managed precisely.
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