EET EES OBVIOUS (Hindsight Bias)
The tendency to believe that something was obvious after learning it, failing to recognize that it was not obvious before. This cognitive bias leads people to overestimate their own foresight and undervalue the difficulty of original discovery.
THE IDEA
“EET EES OBVIOUS”
Digression: when I tell people the story of Edmond Halley and the price of annuities, I often get interrupted: “But it’s obvious that you should charge younger people more!”
It is not obvious. Rather, it is obvious if you already know it, as modern people do. But the fact that people who administered annuities failed to make this observation, again and again, is proof that it’s not actually obvious. Mathematics is filled with ideas that seem obvious now—that negative quantities can be added and subtracted, that you can usefully represent points in a plane by pairs of numbers, that probabilities of uncertain events can be mathematically described and manipulated—but are in fact not obvious at all. If they were, they would not have arrived so late in the history of human thought.
This reminds me of an old story from the Harvard math department, concerning one of the grand old Russian professors, whom we shall call O. Professor O is midway through an intricate algebraic derivation when a student in the back row raises his hand.
“Professor O, I didn’t follow that last step. Why do those two operators commute?”
The professor raises his eyebrows and says, “Eet ees obvious.”
But the student persists: “I’m sorry, Professor O, I really don’t see it.”
So Professor O goes back to the board and adds a few lines of explanation. “What we must do? Well, the two operators are both diagonalized by . . . well, it is not exactly diagonalized but . . . just a moment . . .” Professor O pauses for a little while, peering at what’s on the board and scratching his chin. Then he retreats to his office. About ten minutes go by. The students are about to start leaving when Professor O returns, and again assumes his station in front of the chalkboard.
“Yes,” he says, satisfied. “Eet ees obvious.”
When to use it
In education, teachers can use this bias to illustrate why students should not feel foolish for not grasping a concept immediately.
In decision analysis, when reviewing past decisions, avoid claiming outcomes were obvious to prevent hindsight bias from distorting lessons learned.
In innovation, understanding this bias can encourage patience and reduce frustration when new ideas are not immediately accepted as obvious.
FROM THEORY TO EVERYDAY LIFE
In practice
Edmond Halley and Annuity Pricing
Edmond Halley discovered that younger people should pay more for annuities because they would receive payments for longer. Modern listeners often say this is obvious, but historical administrators had not realized it, showing it was not obvious at the time.
Professor O’s Algebraic Derivation
A student questioned why two operators commute. Professor O initially dismissed it as obvious, but after struggling to explain it, he retreated to his office and confirmed the step was indeed non-trivial. Experts often overestimate how obvious their knowledge is.
A MOMENT TO REFLECT
Put it to work.
Think of a time you learned something new and then thought, 'That was obvious.' In hindsight, what made it seem obvious after learning it?
List three historical discoveries that seemed obvious after their invention but were not obvious before. What does this say about the nature of discovery?
How might the 'it's obvious' bias affect your judgment when evaluating others' decisions or your own past predictions?
CONTINUE THE CONVERSATION
Source texts
- How Not to Be Wrong The Power of Mathematical Thinking (Ellenberg, Jordan)