Observe the details
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, :
"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.
