Making It So

Published in The Serpentine Muse, vol. 27 issue 1

How does Sherlock Holmes perform his unusual feats of deduction? He is a genius, of course, but to dismiss the question there is to willingly fail to understand. This paper will explore the question of Holmes’ abilities through the lens of contemporary cognitive neuroscience. For this discussion we will take examples from “The Naval Treaty,” though there is no significance to be drawn from that. It merely provides a few excellent instances of Holmes doing what he does best.

In “The Naval Treaty,” Holmes and Watson are summoned by Watson’s old school friend Phelps. Upon arriving at Phelps’ house, Holmes immediately deduces that the man who meets them is not Phelps’ relative. He does this, as the man realizes, by noticing the monogram on the man Harrison’s coat.

I begin with this detail because it is in keeping with the idea that “we see, but we do not observe.” The detail of a monogram is disregarded by most of us, but Holmes notices it and derives its significance. How?

The various filter theories of attention suggest that the world is full of details that our senses take in but our brain disregards. Classroom examples of this are the texture of clothing on one’s body, or the ubiquitous hum of florescent lights. These stimuli are ever present in our environment, but the brain dismisses them as unimportant. If we paid attention to all the stimuli in the world, we would be overwhelmed, for our brains do not have enough attentional capacity to handle it all. Instead, our senses take in all the details about the world, and the brain decides what is and is not important, and gets rid of the latter before sending the former on to the conscious mind. So goes the monogram, for most of us. Holmes, however, notices this detail. He has trained his brain to accept details that most of our brains do not. Instead of most of us “seeing but not observing,” Holmes in fact sees what the rest of us do not.

There is more to this process than an expanded attention. Holmes not only notices the monogram but understands its significance. Now, we all understand the significance of a monogram: it shows the initials of the owner. Holmes makes use of this knowledge to deduce something about that owner’s identity, namely, that he is unrelated to their client. This is a conclusion that any of us might come to, upon consideration. But to see the monogram, understand that a monogram is indicative of the owner’s identity, and compare that identity to the client’s, in the space of moments is a feat attributable only to Holmes. To explain it, we must invoke several notions from cognitive neuroscience.

First, fast visual processing. It takes an entire 40 milliseconds for a stimulus to be fully processed by the visual cortex and identified as an object. What if Holmes processes visual information unusually quickly? An extra 10 milliseconds would be enough to give him a significant advantage over those with more ordinary brains. This speed could be attained by extra thickness in the layer of myelin, a fatty sheath, that coats the axons, or connecting arms, of brain cells. The myelin insulates the axons and speeds the conduction of electrical energy down these connections. The thicker the myelin, the faster the conduction. It is the decrease of myelin that results in slowed motion and cognition in diseases such as MS.

We may also theorize that Holmes has unusually dense connections between his visual cortices, where objects are recognized by the brain, and his association cortices, where information about those objects is stored. The brain sends information about a recognized object to these association areas, where that visual information is matched with any other knowledge about that object, what psychologists call semantic information. Holmes therefore arrives at knowledge about monograms more swiftly than others do.

Holmes is also an expert. It is well known that experts’ brains function differently than ordinary brains. An expert in chess sees patterns where others see pieces. An expert in cars or flowers or birds identifies small details about type where the rest of us see merely cars or flowers or birds. We are all experts in the recognition of faces, and can recognize thousands of distinct individuals. The part of our brain devoted to the processing and recognition of faces is highly specialized, with individual neurons signaling specially for specific faces. As an expert, Holmes has trained himself in the recognition of items other than faces – items such as monograms. When Holmes sees a monogram, the “monogram cells” in the parts of his brain devoted to criminal investigation send their signals, and trigger the knowledge of information about monograms – information that may be used to solve a case.

These expertise effects are among the most prominent of cognitive differences between Holmes’ brain and our brains. Holmes knows what details to inquire of Phelps because of his expertise. Over long practice, he has learned what details of a criminal scene are of importance. Because of this practice, his abilities are distinct from those of other professionals such as the police – Holmes notices that the detective in the “Naval Treaty” case is young and new to his job. This man has not had time to become an expert in criminal investigation, and because he will have ordinary cases throughout his career, will not become the same sort of expert in extraordinary crime that Holmes is.

Leaving expertise effects, I finally wish to point out that after interviewing Phelps, Phelps’ uncle, and placing an advertisement, Holmes declares that he will do nothing else about the case on that day. Even brain cells need their rest, and the willingness to take rest is as much the mark of a genius as the expertise effects previously described. After a brain cell signals, it enters a refractory period in which it takes much more stimulation to cause that cell to signal again. After a period of rest, the cell returns to its original state. This effect is cumulative; if the cell is forced to fire during its refractory period, the subsequent refractory period is longer and it takes even stronger stimulation to force the cell to signal again. Resting one’s brain cells is therefore a way of returning them to a state in which they can be easily stimulated, leading to faster and better cognition.

To conclude, we may attribute at least part of Holmes’ genius to expertise effects that are explained by contemporary cognitive neuroscience. Some additional effects are explained by Holmes’ willingness to take rest at times, which works in harmony with the functioning of the brain. We may learn from this that while we may not entirely aspire to Holmes’ genius, we can train our brains to become experts in our own chosen fields, and follow his example as we often wish to do.