Sherlock Holmes IQ

DeductionSolving new problems from thin information

10/10

StrategyMulti-step plans that account for other minds

8/10

KnowledgeDepth and breadth of what they know

7/10

InventionBuilding or devising something genuinely new

6/10

AdaptabilityRecovering when the plan breaks

9/10

Reading peopleUnderstanding what other people want and will do

9/10

1. Reading Watson's past on first meeting

   Moderate evidence

   A Study in Scarlet

   On being introduced to Dr. Watson, Holmes remarks that he has been in Afghanistan, and later lays out the chain: a doctor's manner but a military bearing, a tanned face with pale wrists, an injured arm held stiffly. He reaches the conclusion without being told anything. It is the founding example of the method, observations turned into a conclusion by explicit steps, and it matters cognitively because the reasoning is shown and can be checked. It is a small case, so we treat it as a demonstration of the method rather than a great feat.

2. The dog that did nothing

   Strong evidence

   Silver Blaze

   In the case of a missing racehorse and a dead trainer, Holmes points to what did not happen: the stable dog made no sound in the night. From that absence he concludes the visitor was someone the dog knew, which points away from the stranger the police have arrested. Reasoning from a missing fact is harder than reasoning from a present one, and it is why this story is so often cited. It shows real abstract inference, not observation alone.

3. Working out the Speckled Band

   Strong evidence

   The Adventure of the Speckled Band

   Holmes examines a bedroom and notices a bell rope that rings nothing, a ventilator opening into the next room, and a bed fixed to the floor. He infers that a dangerous animal is being sent through the ventilator, waits in the dark room to be sure, and drives the creature back onto its owner. It requires connecting several odd details into one mechanism, then predicting the criminal's next move. It is a clean, well-cited example of deduction and planning working together.

4. Facing Professor Moriarty

   Strong evidence

   The Final Problem

   Holmes traces a network of crime to a single mastermind, Professor Moriarty, and then spends the story dodging his organization while preparing to bring it down. The confrontation at the Reichenbach Falls leaves both men apparently dead. It shows Holmes reasoning about an intelligent opponent rather than a puzzle. The contest is an even one, which is why we do not push him past the 160s, and it is the strongest case for his adaptability.

5. Returning and springing a trap

   Moderate evidence

   The Adventure of the Empty House

   After his apparent death, Holmes returns and catches Colonel Sebastian Moran, the killer of a young nobleman, by staging a scene: a wax bust of himself in the window, a rifleman's likely perch across the street, and a patient wait in the dark. The plan depends on how one specific person will react. It shows the same skill as the earlier stories in a longer setting, and it is a good example of strategy that accounts for a hostile mind.

1. Outwitted by Irene Adler

   A Scandal in Bohemia

   Holmes tries to recover a compromising photograph, and a staged commotion does reveal where Irene Adler keeps it. But she has already recognized him in disguise, and by morning she has left the country with the photograph. Holmes treats her with lasting respect, but it is a full defeat by someone who out-planned him.

2. Chosen ignorance

   A Study in Scarlet

   Holmes says he does not know or care that the Earth goes around the Sun, arguing that useless facts crowd out useful ones. It is a deliberate rule, but it means his knowledge is narrow outside his specialties. A reader could count it as a real limit on breadth.

3. Wrong about a case

   The Adventure of the Yellow Face

   Holmes builds a confident theory about the strange tenant of a cottage, and it turns out to be wrong. He admits it and asks Watson to whisper a reminder of the case if he ever grows overconfident. It is honest and rare, and it shows that his method can fail when he decides too early.

Sherlock Holmes' fan estimate of 165 falls in the profoundly gifted IQ range. See what an IQ of 165 means, or place it on the IQ chart.

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