Sherlock Holmes met Watson for the first time and told him with utter certainty, “You have been in Afghanistan, I perceive.” and Watson responds – “How on earth did you know that?“. Sherlock Holmes explains how he deduced it.

I knew you came from Afghanistan. From long habit the train of thoughts ran so swiftly through my mind that I arrived at the conclusion without being conscious of intermediate steps. There were such steps, however. 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 that 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.” The whole train of thought did not occupy a second. I then remarked that you came from Afghanistan, and you were astonished.

Holmes thought process astonished me and I kept asking myself how did he do it? Recently I read the book Mastermind: How to Think Like Sherlock Holmes by Maria Konnikova. In this book the author tells that Holmes uses scientific method of thinking.

Scientific method in a nutshell is: observe; hypothesize (or imagine); test and deduce; and repeat. Before looking into the details of each steps we need to understand few basics things about our brain.

The Brain Attic

Our brain is like an empty attic and it is our responsibility to stock it with the furniture of our choice.  Holmes tells Watson that

A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it. Now the skillful workman is very careful indeed as to what he takes into his brain attic.

Our memory is divided into short-term and long-term memory. When we see something first it is processed by the brain and stored in the hippocampus. This is the first entry point to the brain attic.

From there, the stuff that you either actively consider important or that your mind somehow decides is worth storing, based on past experience and your past directives (i.e., what you normally consider important), will be moved to a specific box within the attic, into a specific folder, in a specific compartment in the cortex – the bulk of your attic’s storage space, your long-term memory. This is called consolidation.

This is the reason why we should work on what really turns us on. We will be mindful and motivated on things that we really care about. This will enable our brain to do better consolidation and store information in the long-term memory.

The information stored in the brain is retrieved using associative activation.

When you need to recall a specific memory that has been stored, your mind goes to the proper file and pulls it out. Sometimes it pulls out the file next to it, too, activating the contents of the whole box or whatever happens to be nearby – associative activation … Some things gets stored; some are thrown out and never reach the main attic. What’s stored is organized according to some associative system – your brain decides where a given memory might fit – but if you think you’ll be retrieving an exact replica of what you’ve stored, you’re wrong. Contents shift, change, and re-form with every shake of the box where they are stored.

This is one of the reason why you should be skeptical when you are recollecting past incidents from your memory.

Our minds operate on a two-system basis. One is called as System Watson and the other one is System Holmes.

To understand the effect of System Watson try to answer the following questions. Do not take a lot time to think about these questions. Make a mental note of the initial answer that comes to your mind.

  1. A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball. How much does the ball cost?
  2. If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?
  3. In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of the lake?

If you are like most people then you would have answered $0.10 for question one, 100 minutes for question two and 24 days for question three. But these answers are incorrect. The correct answers are $0.05, 5 minutes and 47 days. The reason most of us could not get the correct answer is because of System Watson. This system is reflexive and jumps to conclusions and can lead us to come up with incorrect answers. This is our default mode of operation. You should be very careful to not take important decisions under its influence.

Can you multiply 29 * 77 in your head? You can but it requires some active effort and you need to concentrate for some time. You used System Holmes for this calculation. This system is reflective, more thorough and logical in nature. It is very hard to be in this state all the times. But you should use this system for making important decisions in life.

Before you begin to apply the scientific method you need to be mindful, attentive and engage system Holmes.

1. Observe

Seeing is not observing. Read all the three sentence given below.


Did you see anything odd in these sentences. If you have observed these sentences carefully you would have noticed that “the, a, the” is repeated twice in these sentences. If you do not believe me observe it carefully this time. Click here to view the repetition marked in red. This exercise should have clarified the difference between seeing and observing.

For you to observe you need to be attentive. Attention is a limited resource. Paying attention to one thing necessarily comes at the expense of another. This means we cannot allocate our attention to multiple things at the same time and expect quality output from all of them. Our brain is not good in multitasking. Take a look at the video and it should summarize what most of us do.

Sometimes we focus on one element in a scene and fail to notice all other important elements in the scene. This phenomenon is called as attentional blindness. Watch the video to experience this.

You should not observe something with a preconceived notions. Philosopher Francis Bacon writes – The human understanding when it has once adopted an opinion (either as being the received opinion or as being agreeable to itself) draws all things else to support and agree with it.

An observant mind, an attentive mind, is a present mind. It is a mind that isn’t wandering. It is a mind that is actively engaged in whatever it is that it happens to be doing. And it is a mind that allows System Holmes to step up, instead of letting System Watson run around like crazy, trying to do it all and see it all.

2. Hypothesize (Imagine)

After observation we immediately move to the deduction phase. From observation we should imagine before deducing anything. Why should we imagine?  Richard Feynman tells that

It is surprising that people do not believe that there is imagination in science. Not only is that view patently false, but it is very interesting kind of imagination, unlike that of the artist. The great difficulty is in trying to imagine something that you have never seen, that is consistent in every detail with what has already been seen, and that is different from what has been thought of; furthermore, it must be definite and not a vague proposition. This is indeed difficult.

Much of the imagination is about making connections that are not obvious at first. It requires creativity and knowledge of basic building blocks (mental models) across several disciplines. Creativity is hard. Why? Human brain loves certainty and it avoids unknowns. Creativity requires navigating the unknown and hence it is not easy. Also we hate to fail. Creativity requires you to meet failure several times.

Consider the following problem. Can you solve it?

Given a book of matches, a box of thumbtacks, and a candle, how can you fix the candle to the wall so that its wax won’t drip onto the table below?


Several people could not solve this problem. Click here to view the solution.

Pin the box to the wall, put the candle in the box, and light it.

Why don’t so many people see that alternative? They forget that between observation and deduction there lies an important mental moment. They take the hot System Watson route – action, action, action – underestimating the crucial need for the exact opposite: a moment of quiet reflection. And so they understandably go at once for the most natural or most obvious solutions. The majority of people in this situation do not see that something obvious – a box of tacks – might actually be something less obvious: a box and tacks.

In experiments, Gestalt psychologist Karl Duncker found that most subjects instead tried to pin the candle directly to the wall or to use melted wax to affix it there (neither worked). Duncker called this “functional fixedness” — a “mental block against using an object in a new way that is required to solve a problem.” In this case, subjects had “fixated” on the box’s function as a container, which prevented them from considering it as a platform. If the box was empty at the start of the experiment, they were more likely to find the correct solution.

Creativity is not all or nothing proposition. It is not innate. It is a muscle which gets bigger with practice. If you avoid the fear of failure and stay calm in unknown territories you will do better. Here is one simple solution.

Our natural mindset may well be holding us back, but a simple prime is enough to cue it in a very different indeed. Works of art on the walls do the trick, too. The color blue. Pictures of famous creative thinkers, Happy faces. Happy music. (In fact, almost all positive cues.) Plants and flowers and scenes of nature. All of these tend to boost our creativity with or without our awareness.

Distancing away from the problem at hand helps us to come out with creative solutions. Meditation is one way to distance away from the problem.

Have you played yes-or-no riddle games? One person knows the answer to a simple riddle and the rest of the group will try to guess the solution by asking questions that require only a yes or no answer. This game forces you to separate observation from deduction and increases your thought process. This problem reminds me of Charlie Munger talk on – Academic Economics: Strengths and Faults.

Generally I recommend and use in problem solving cut-to-the quick algorithms, and I find you have to use them both forward and backward. Let me give you an example. I irritate my family by giving them little puzzles, and one of the puzzles that I gave my family not very long ago was when I said, “There’s an activity in America, with one-on-one contests, and a national championship. The same person won the championship on two occasions about 65 years apart.” “Now,” I said, “name the activity,” (Pause). Again, I don’t see a lot of light bulbs going on. And in my family not lot of light bulbs were flashing. But I have a physicist son who has been trained more in the type of thinking I like. And he immediately got the right answer, and here’s the way he reasoned:

It can’t be anything requiring a lot of hand-eye coordination. Nobody 85 years of age is going to win a national billiards tournament, much less a national tennis tournament. It just can’t be. Then he figured it couldn’t be chess, which this physicist plays very well, because it’s too hard. The complexity of the system, the stamina required are too great. But that led into checkers. And he thought, “Ah ha! There’s a game where vast experience might guide you to be the best even though you’re 85 years of age.”

And sure enough that was the right answer.

3. Deduction

You have gathered all the data (observe) and considered all the possibilities (imagine) and it is time to deduce. Looks simple but it is not. Our brain likes simplicity. It likes to find causes behind every event even if there is none. It does not like uncertainty, chance and randomness as it threatens our ability to explain things. This often leads us to make incorrect deductions.

We think a coin is more likely to land on heads if it has fallen on tails for a number of times (the gambler’s fallacy), forgetting that short sequences don’t necessarily have the fifty-fifty distribution that would appear in the long term. Whether we’re explaining why something has happened or concluding as to the likely cause of an event, our intuition often fails us because we prefer things to be much more controllable, predictable, and causally determined than they are in reality.

I came across the news snippet recently about the Indian stock market.

Markets came off their day’s highs in late morning trades as investors booked profits at higher levels after the Sensex surged to an all-time high in early trades today.

Look at the bolded words ‘investors booked profits’. Is this the actual reason the market came off their day’s highs? As readers we want to know the reason why the market came of the day’s high. The writer of this article understands this and he is fitting in a story. In fact you can write ‘the sun was shining’ or ‘it was cloudy’ it would not have mattered.

Consider the following description about Linda

Linda is thirty-one years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in antinuclear demonstrations.

Which of the alternatives is more probable about Linda?

  1. Linda is a bank teller.
  2. Linda is a bank teller and is active in the feminist movement.

If you have answered option 2 then you have made a logical error like 85% to 90% undergraduates of major universities. This mistake is called as conjunction fallacy. In this we judge a conjunction of two events (here, bank teller and feminist) to be more probable than one of the events (bank teller) in a direct comparison.

If you do not believe me take a look at the venn diagram.


If there are 1000 people and 20% of them are bank tellers and 2% of them are active in feminist movement then we will have 1000 * 0.2 = 200 bank tellers and 1000 * 0.2 * 0.02 = 4 feminist bank teller. Hence the likelihood of bank teller is much higher.

You need to understand these fallacies and avoid them. If you want to increase the odds of deducing correctly you need to separate the crucial from the incidental.

There is too much information to begin with, too many details to be able to start making them into any sort of coherent whole, separating the crucial from the incidental.

To put it in Holmesian terms

You lay out your chain of reasoning and test possibilities until whatever remains (improbability aside) is the truth: “That process starts upon the supposition that when you have eliminated all the which is impossible, then whatever remains, however improbable, must be the truth.

Closing Thoughts

I really enjoyed reading the book Mastermind: How to Think Like Sherlock Holmes. It is worth your time. Reading this book gave me a feeling of learning directly from Sherlock Holmes, Richard Feynman and Daniel Kahneman.

Scientific method helps us to understand the world better. It can tells us why things are the way they are. It is hard but not impossible.

To summarize

An observant mind, an attentive mind, is a present mind. It is a mind that allows System Holmes to step up. Imagination is about making connections from multiple disciplines. Creativity is hard but with practice we can get better at it. Do not fear failure. For deducing correctly you need to separate crucial from the incidental.


3 thoughts on “Mastermind

  1. Hi Jana! I’ve been following your blog for some time now and I really enjoy your posts, they are well thought through and always insightful.

    In this post, you give an impression of overwhelmingly favoring System 2 (System Holmes). I understand where you’re coming from, and agree about the importance of System Holmes, but I also think you have much underappreciated System 1 here.

    I’m referring to phrases like “It is very hard to be in this state all the times. But you should use this system for making important decisions in life.”. Why would you want to be in System 2 all the time? This would be totally inefficient. Remember that System 2 is very resource consuming. You wouldn’t be able to even get out of bed in the morning if you had to ponder over everything and every step. One of the great advantages of this dual-system is that when you become really good at something, you move it to system 1. For example, a really good tennis player doesn’t use system 2 to return a ball. He can do really complicated and amazing things without having to “think” about them. In fact, in this case, System 2 normally gets in the way: this is one of the reasons great sportsmen “choke”.

    Going back to your quote: “you should use this system for making important decisions in life”. Obviously you are referring to decisions which by their nature can be pondered and are not urgent. If a lion is running towards you, I wouldn’t spend a lot of time thinking. And I would also consider this a pretty important decision moment.

    So the great advantage of System1 is that it always operates and is extremely energy efficient. This is also it’s great disadvantage. It will give you answers even if it doesn’t really know them. One of the great things about System 2 is that it is able to return the answer “I don’t know”, which by the way is the most common answer in science.

    All this is not criticism to your post. I just wanted to share some thoughts that your post has provoked 🙂

    Take care,


    • Hi Andres,

      Thanks for all your comments.
      Yes I agree with all your points and I am not against System 1.

      It is there for a reason. In order to navigate the complex world, we need to take decisions effortlessly and that is what System 1 is good at.

      Without System 1 experts in their field would not be able to do all the wonders they are doing. But it did not happen to them on day 1. They put enormous hours of practice and in the process learnt a lot. This was because of System 2. Once these skills became second nature it got into System 1.

      Similarly for applying scientific method you need to start using System 2 and once it becomes second nature then you can leverage the powers of System 1.


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