In the Arthur Conan Doyle story, “The Silver Blaze,” Sherlock Holmes discusses the theft of a race horse from a country estate that is guarded by a fierce watch dog.
“Is there any point to which you would wish to draw my attention?”
Holmes: “To the curious incident of the dog in the night-time.”
“The dog did nothing in the night-time.”
Holmes: “That was the curious incident.”
Holmes later explains how the “dog that didn’t bark” helped him to solve the crime:
I had grasped the significance of the silence of the dog, for one true inference invariably suggests others… A dog was kept in the stables, and yet, though someone had been in, and had fetched out a horse, he had not barked enough to arouse the two lads in the loft. Obviously the midnight visitor was someone whom the dog knew well.
This is an example of abductive reasoning: an inference is made based on known facts, in an effort to explain them. It certainly sounds good here. Holmes is working on the premise that because (a) dogs bark loudly at strangers, but not at people they know; and (b) the dog didn’t bark loudly, if he barked at all; then (c) the dog knew the intruder. This is how many detectives and police officers work out a problem. But this reasoning contains fundamental flaws, claims Dr. Robin Bryant, Director of Criminal Justice Practice at Christ Church University, in Canterbury, England, a criminologist with an expertise in how detectives think.
With the new season of the hugely-popular Sherlock television series just kicking off, it seems like an apt time to consider the question: outside the realm of fiction, where Holmes’ “deductions” all seem to end up correct, would Conan Doyle’s detective be considered a sound, logical thinker in today’s world of policing?
Check out the rest of this article of mine, published this weekend in The Daily Beast…