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Cognitive Biases

Serotonin and Randomness

A run of success can increase confidence even when luck contributed heavily to the results. Taleb argues that this can reinforce both the winner’s belief in their ability and other people’s impression of competence. He proposes serotonin as part of the explanation, but the behavioral lesson does not establish a particular biological mechanism.

THE IDEA

Serotonin and Randomness

Can we judge the success of people by their raw performance and their personal wealth? Sometimes—but not always. We will see how, at any point in time, a large section of businessmen with outstanding track records will be no better than randomly thrown darts. More curiously, and owing to a peculiar bias, cases will abound of the least-skilled businessmen being the richest. However, they will fail to make an allowance for the role of luck in their performance.

Lucky fools do not bear the slightest suspicion that they may be lucky fools—by definition, they do not know that they belong to such a category. They will act as if they deserved the money. Their strings of successes will inject them with so much serotonin (or some similar substance) that they will even fool themselves about their ability to outperform markets (our hormonal system does not know whether our successes depend on randomness). One can notice it in their posture; a profitable trader will walk upright, dominant style—and will tend to talk more than a losing trader. Scientists found out that serotonin, a neurotransmitter, seems to command a large share of our human behavior. It sets a positive feedback, the virtuous cycle, but, owing to an external kick from randomness, can start a reverse motion and cause a vicious cycle. It has been shown that monkeys injected with serotonin will rise in the pecking order, which in turn causes an increase of the serotonin level in their blood—until the virtuous cycle breaks and starts a vicious one (during the vicious cycle failure will cause one to slide in the pecking order, causing a behavior that will bring about further drops in the pecking order). Likewise, an increase in personal performance (regardless of whether it is caused deterministically or by the agency of Lady Fortuna) induces a rise of serotonin in the subject, itself causing an increase of what is commonly called “leadership” ability. One is “on a roll.” Some imperceptible changes in deportment, like an ability to express oneself with serenity and confidence, make the subject look credible—as if he truly deserved the shekels. Randomness will be ruled out as a possible factor in the performance, until it rears its head once again and delivers the kick that will induce the downward spiral.

A word on the display of emotions. Almost no one can conceal his emotions. Behavioral scientists believe that one of the main reasons why people become leaders is not from what skills they seem to possess, but rather from what extremely superficial impression they make on others through hardly perceptible physical signals—what we call today “charisma,” for example. The biology of the phenomenon is now well studied under the subject heading “social emotions.” Meanwhile some historian will “explain” the success in terms of, perhaps, tactical skills, the right education, or some other theoretical reason seen in hindsight. In addition, there seems to be curious evidence of a link between leadership and a form of psychopathology (the sociopath) that encourages the non-blinking, self-confident, insensitive person to rally followers.

People have often had the bad taste of asking me in a social setting if my day in trading was profitable. If my father were there, he would usually stop them by saying “never ask a man if he is from Sparta: If he were, he would have let you know such an important fact—and if he were not, you could hurt his feelings.” Likewise, never ask a trader if he is profitable; you can easily see it in his gesture and gait. People in the profession can easily tell if traders are making or losing money; head traders are quick at identifying an employee who is faring poorly. Their face will seldom reveal much, as people consciously attempt to gain control of their facial expressions. But the way they walk, the way they hold the telephone, and the hesitation in their behavior will not fail to reveal their true disposition. On the morning after John had been fired, he certainly lost much of his serotonin—unless it was another substance that researchers will discover in another decade. One cab driver in Chicago explained to me that he could tell if traders he picked up near the Chicago Board of Trade, a futures exchange, were doing well. “They get all puffed up,” he said. I found it interesting (and mysterious) that he could detect it so rapidly. I later got some plausible explanation from evolutionary psychology, which claims that such physical manifestations of one’s performance in life, just like an animal’s dominant condition, can be used for signaling: It makes the winners seem easily visible, which is efficient in mate selection.

When to use it

  • Evaluating investment managers: look beyond recent performance and consider whether returns are due to market trends or genuine skill.

  • Making hiring decisions: avoid being swayed by a candidate's confident posture and instead assess their actual track record and decision-making process.

  • Self-reflection: after a success, pause to analyze the role of luck before attributing it solely to your abilities.

  • Team leadership: Separating a leader’s confidence after recent successes from evidence about the quality of their decisions.

FROM THEORY TO EVERYDAY LIFE

In practice

01

Lucky Trader's Overconfidence

A hypothetical trader enjoys a lucky streak, becomes more confident, and attributes the gains to skill. That confidence may encourage greater risk-taking. The example illustrates mistaken attribution; it does not measure the trader’s serotonin or establish what caused the change in demeanor.

02

CEO Hailed as Visionary

A CEO leads a company through a period of favorable market conditions. The company's success is largely due to external factors, but the CEO's confident demeanor and charisma lead the board and media to attribute the success to his strategic genius. He is praised as a visionary, while the role of randomness is ignored.

✳

A MOMENT TO REFLECT

Put it to work.

  1. Can you think of a personal success that might have been more due to luck than skill? How did you feel afterward?

  2. When someone appears confident, what evidence do you use to assess their competence independently of that impression?

  3. What steps can you take to distinguish between your own skill and randomness in your achievements?

CONTINUE THE CONVERSATION

Source texts

  • Fooled by Randomness The Hidden Role of Chance in the Markets and in Life (Nassim Nicholas Taleb)
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