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Notes on Fooled by Randomness (Nassim Taleb)

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Notes on Fooled by Randomness (Nassim Taleb)

Incerto Book 1

Devin Baker
Aug 18, 2020
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Notes on Fooled by Randomness (Nassim Taleb)

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“This book is the synthesis of, on one hand, the no-nonsense practitioner of uncertainty who spent his professional life trying to resist being fooled by randomness and, on the other, the aesthetically obsessed, literature-loving human being willing to be fooled by any form of nonsense that is polished, refined, original, and tasteful. I am not capable of avoiding being the fool of randomness; what I can do is confine it to where it brings some aesthetic gratification”

“We favor the visible, the embedded, the personal, the narrated, and the tangible; we scorn the abstract. Everything good (aesthetics, ethics) and wrong (Fooled by Randomness) with us seem to flow from it”

“Recall that epic heroes were judged by their actions, not by the results. No matter how sophisticated our choices, how good we are at dominating the odds, randomness will have the last word. We are left only with dignity as a solution - dignity defined as the execution of a protocol of behavior that does not depend on the immediate circumstance”

C.P. Cavafy in “The God Abandons Antony”: Antony is defeated and betrayed, and is told not to mourn his luck, not to enter denial, not to believe his ears and eyes are deceiving him.

  • “Just listen while shaken by emotion but not with the coward’s imploration and complaints”

  • While shaken by emotion: there is nothing wrong with emotions - what is wrong is not following the heroic, dignified path

“Start stressing personal elegance at your next misfortune”

“Try not to play victim when diagnosed with cancer (hide it from others and only share the information with the doctor - it will avert the platitudes and nobody will treat you like a victim worthy of their pity; in addition, the dignified attitude will make both defeat and victory feel equally heroic). Be extremely courteous to your assistant when you lose money. Try not to blame others for your fate, even if they deserve blame. Never exhibit any self-pity, even if your significant other bolts with the handsome ski instructor or the younger aspiring model. Do not complain….The only article Lady Fortuna has no control over is your behavior”

“Don’t do to others what you don’t want them to do to you; the rest is just commentary”


  • Do not assume positive events were due to skill - assume they could have been luck and proceed accordingly

  • Consider all possible outcomes (both up and down) - don’t just assume that because something happened that it was likely to

    • e.g., “If I did this 1 million times, what is the outcome that would happen the most?”

    • Focus on inputs, not outputs (since outputs can be affected by randomness)


  • $10 million earned through Russian roulette does not have the same value as $10 million earned through the diligent and artful practice of dentistry

    • One’s dependence on randomness is greater than the other

  • Reality is far more vicious than Russian roulette

    • It delivers the fatal bullet rather infrequently, like a revolver that would have hundreds or thousands of chambers instead of six

    • After a few dozen tries, one forgets about the existence of a bullet, under a numbing false sense of security

    • The risk is undefined (unlike Russian roulette)

    • We struggle with appreciation of preparing for an abstract downside that doesn’t end up happening

  • Our tendency to make and unmake prophets based on the fate of the roulette wheel is symptomatic of our ingrained inability to cope with the complex structure of randomness prevailing in the modern world


  • It is not natural for us to learn from history - our tendency is to have to experience it for ourselves

    • e.g., Children will cease to touch a burning stove only when they are themselves burned; no possible warning from others can lead to cautiousness

  • We also struggle to learn from our own history

    • We don’t learn that our emotions from past events are short-lived (positive or negative)

    • Yet, we continually retain bias that purchases will bring long-lasting happiness or setback will cause severe or prolonged distress when these feelings were short-lived in the past


  • There is nothing wrong with a risk-taker taking a hit, provided that one declares that they are a risk-taker rather than that the risk being taken is non-existent

    • Those that “blow up,” or those that believe the risk taken is non-existent, think that they know enough about the world to reject the possibility of the adverse event taking place; there’s no courage in taking the risk, just ignorance

    • They often make claims that “these times are different”

    • They’re unable to see that these “crash” experiences have been lived and documented many times before


  • A mistake isn’t to be determined by the outcome, but in light of the information to that point

    • We often judge by hindsight bias (overestimation of what one knew at the time, due to being able to see the actual result)


  • Unlike hard science, history can’t lend itself to experimentation

    • But, over the long run, it delivers most of the possible scenarios

  • Ergodicity: long sample paths end up resembling each other; they revert to their long-term properties

    • Unlucky but skillful people eventually rise

    • Lucky fools converge to the unlucky fool

  • Some new information is better than past information, but the average of distilled past information is better

    • Focus on distilled past information (first principles) (this especially applies to reading)

    • The opportunity cost of missing an extraordinary new thing is low vs. the toxicity of all the garbage one has to go through to get to the jewels

  • “If there is anything better than noise in the mass of ‘urgent’ news pounding us, it would be like a needle in a haystack”

    • The ratio of undistilled information is rising; the need to capture attention > signal

    • If an event is important enough, you will hear about it


  • Over short time increments, you observe variability (noise), not returns (signal)

    • The higher the frequency of observation, the more volatility (noise) you consume

    • Plus, the volatility results in you feeling emotional highs and lows (which are 2.5x worse physiologically) every step of the way

      • Higher frequency exacerbates lows > highs

  • It is less unpleasant to lose $100 once than lose $1 one hundred times

    • So, making $1 per day for a long time then losing it all is actually pleasant from a hedonic standpoint, although nonsensical economically


  • “We do not need to be rational and scientific when it comes to the details of our daily life - only in those that can harm us and threaten our survival. Modern life seems to invite us to do the exact opposite - become extremely realistic and intellectual when it comes to such matters as religion and personal behavior, yet as irrational as possible when it comes to matters ruled by randomness (say, a portfolio or real estate investments).”

  • Yiddish saying: “If I am going to be forced to eat pork, it better be of the best kind”

    • If I’m going to be fooled by randomness, it better be of the beautiful (and harmless) kind

  • How to operate as humans with all this uncertainty?

    • “Satisficing”: stop at near-satisfactory solutions; otherwise, you could spend eternity reaching small conclusions “perfectly”

    • Use heuristics: practical methods or rules

      • Beware that these are prone to bias


  • It doesn’t matter how likely an event is to happen - what matters is how much is made in that scenario

    • Probability doesn’t matter, probability x outcome matters

    • Nobody takes home a check linked to how often they’re right - what you have is a profit or loss

  • An event, although rare, that brings large consequences cannot be ignored

    • You cannot remove the outliers if the impact is large - you have to take them into account

  • Rare events are always unexpected, otherwise they would not occur

    • If you expected them, you would prepare and avoid them

  • Because negative variations cause more emotional pain than positive, people are drawn to strategies that experience rare but large variations

    • “Pushing randomness under the rug”

    • They will aim for less frequency of variation, which by nature means the unexpected will happen

    • People are more sensitive to presence or absence of stimulus rather than its magnitude


  • Statistics fails us when distributions are not symmetric

    • Statistics = information

  • By nature of asymmetry, we collect more information on the more likely (i.e., frequent) event, so we get more confident in predicting the frequent event (confirmation bias)

    • This makes our understanding that the rare event is less likely than it is

      • Especially if this is greater in magnitude, the effect is severe

  • This is exacerbated by assuming that our knowledge of future events increases by identification of past events

    • But, things change, and past events are not indicative of future events

  • So, statistics fails us

    • It underestimates the likelihood of the rare event

    • It doesn’t take magnitude into account


The problem with empiricism and extrapolation: the Black Swan problem

  • No amount of observations of white swans can allow the inference that all swans are white, but the observation of a single black swan is sufficient to refute that conclusion

  • You can use data (empiricism) to disprove a proposition, never to prove one

  • You can’t make the leap easily from “the market has never gone down 20% in any 3-month period” to saying “it will never”

  • Example:

    • A: “No black swans exist because I looked at 4,000 swans and found none”

    • B: “Not all swans are white”

    • You cannot logically say A, no matter how many swans seen (unless you know with certainty that you’ve seen all available swans)

    • However, it is possible to say B by finding one single counterexample

  • You often hear “it has never happened before”

    • But, when your last “worst case” scenario was experienced, it was a surprise

    • If your past didn’t resemble your past’s past, why should our future resemble our current past?

  • This is the problem of induction (empiricism of the past driving future expectations)


Popper’s response to induction

  • Induction is risky because black swans make empiricism of the past impossible to drive expected future events

  • Popper: only two types of theories

    • A: Theories known to be wrong, as they were tested and rejected (falsified)

    • B: Theories not yet known to be wrong, but exposed to be proved wrong

    • A theory can never be verified

  • So, the only impactful event is if you’re proven wrong (that’s what you have to prepare for)

  • Knowledge doesn’t always increase with more information; it’s also not about what we know, it’s about what we don’t know

  • Taleb speculates in all activities on theories that represent some vision of the world, but stipulates that in carrying out the theory, no rare event should harm him; all conceivable rare events should help; in other words, if he’s proven wrong, it should help

  • Result: an open mind is necessary when dealing with randomness

  • Inductive inferences are easier for the mind

    • Causality (the reduction of the general occurrences to a particular cause) is easier to commit to memory than all the specifics

  • Taleb’s strategy: will use statistics and inductive methods to make aggressive bets, but will not use them to manage risk and exposure

    • Trade on ideas based on some observation (which includes past history), but (like Popper), make sure that the costs of being wrong are limited (don’t determine probability based on past data)

    • Know which events would prove you wrong and allow for them; prepare in this context


  • The extent to which you can translate past success to future success is based on:

    • The randomness of the profession

    • The number of people doing it

  • You don’t see the full sample of all failures (survivorship bias), making things seem likelier than they are

    • The highest performing will be most visible, as the losers don’t show up


  • Biases result in improper understanding of probabilities of historical outcomes

    • Since we extrapolate history to probabilities in the future, this sets us up poorly


Applicable biases

  • Survivorship bias: assuming the probability of success is higher than it is by looking at the survivors (and not those that tried and also failed)

    • You need to take into account the whole population (including those that tried and failed) to understand the validity of track record

    • If population is 10,000 vs. 10, higher chance that somebody will be successful due to randomness

  • Hindsight bias: overestimation of what one knew at the time, due to being able to see the actual result

  • Availability bias: over-estimating the frequency of an event if you can recall an occurrence

    • e.g., The likelihood of a terrorist attack seems greater than it is due to our memory of 9/11

  • Representative bias: gauging the probability that a person belongs to a particular social group by assessing how similar their characteristics are to the “typical” member

  • Simulation bias: playing the alternative scenario; “what would have happened if I sold at the peak”

  • Affect bias: emotions elicited by events determine our view of their probability


  • Avoid backtesting (trying to find any correlation to historical results)

    • You must look for a given relationship, not any

    • You want a narrow lens + time (to get benefits of ergodicity, of time lessening effects of randomness)


  • Path-dependent outcomes throw off probability; the world increasingly has this property - a core component of Extremistan, a world in which we increasingly live (vs. Mediocristan)

    • e.g., Winning makes it more likely to win in the future

    • Drives huge variance and winner-take-all effects

    • Network effects are an example (the more connected the network, the more useful, thus the more likely to succeed)


Two systems of reasoning

  • System 1 (fast thinking): effortless, automatic, emotional, social, personalized

  • System 2 (slow thinking): effortful, self-aware, slow, deductive, asocial, depersonalized


  • Regression to the mean: the larger the deviation from the norm, the bigger the probability of it coming from randomness vs. skill or causality

    • But, if it continues to deviate from the norm repeatedly (due to effects of ergodicity, may be due to a certain cause)

    • e.g., The largest dogs tend to product offspring smaller than them

  • The greater the variance in outcomes, the more causation matters if there is causation (for that, see above - look to ensure continued variance to benefit from ergodicity)

    • e.g., If a 1-month bike race and the winner wins by 3 weeks vs. 1 second, you might start to look for potential causes

  • Look at large percentage changes - unless something changes by more than its usual daily percentage change, the event is likely noise

    • A 7% move can be several billion times more relevant than a 1% move

    • When change in amplitude is small, it’s more likely to be from noise

    • The likelihood of an event being a signal increases exponentially as magnitude increases

  • Trading example

    • $100,000 profit - may assign 2% probability to the cause being a strategy, 98% to noise

    • If $1,000,000 profit - may assign 99% probability tot he cause being a strategy

    • “Since the heart doesn’t agree with the brain, we need to take serious action to avoid making irrational trading decisions, namely, by denying access to a performance report unless it hits a predetermined threshold”

      • Enables you to filter out more of the noise and look for signals (longer time horizon + bigger moves)


  • “Unless you have confidence in the ruler’s reliability, if you use a ruler to measure a table you may also be using the table to measure the ruler”


  • Our behavior is immediately to establish a causal link between two events, even when one may not exist - we are not made to view things as independent from each other


  • “Probability is not about the odds, but about the belief in the existence of an alternate outcome, cause, or motive”


  • Lower-ranking persons are judged on both process and results, while top management is paid on results only

    • The CEO makes a small number of large, non-repeatable decisions, more like a person walking into a casino with a single $1,000,000 bet

    • External factors play a considerably larger role


  • Subway riders are considerably freer than train-riders

    • Higher frequency of trains

    • Uncertainty of schedule

  • A slightly random schedule prevents us from optimizing and being exceedingly efficient, particularly in the wrong things

    • Research on happiness shows that those who live under self-imposed pressure to be optimal in enjoyment of things suffer distress


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