Trading Psychology · Beginner · 5 min
Hindsight bias
You can explain why past charts look more predictable than they were and how a journal written before the outcome protects you.
Obvious, afterwards
Scroll back through any chart and the big moves jump out. The breakout, the crash, the turning point: all of them seem clear. You might think you would have seen them coming.
That feeling is one of the most persistent tricks the mind plays. It makes the past look easier than it was, and the future look easier than it is. For traders, that is a dangerous combination.
The outcome rewrites memory
Hindsight bias is the tendency to believe, after an outcome is known, that it was more predictable than it really was. Psychologist Baruch Fischhoff showed this in 1975 in three experiments with 479 students. People who were told an outcome judged it as more likely than those who were not, and they were largely unaware of how much that knowledge had changed their judgment. They also overestimated what they would have known without it.
The chart above shows why this matters for traders. Seven candles move sideways below a range high. Then the eighth breaks out, and price keeps rising. Seen now, the sideways phase looks like an obvious build-up before the move.
In real time, nobody knew that. The same sideways phase could have broken lower, or kept going sideways for weeks. The last three candles make the first seven look meaningful.
Hindsight bias causes three problems:
- Overconfidence. If the past looks predictable, you expect the future to be predictable too.
- Wrong lessons. You learn the pattern that worked once and forget the times it failed.
- Harsh or soft self-judgment. You blame yourself for "missing the obvious" or credit yourself for "knowing it", when both were uncertain.
Fischhoff argued that this lack of awareness can seriously limit our ability to learn from the past. The fix is not to try harder to remember. It is to record your view before you know the outcome.
Three failed, one worked
A fictional trader looks at the chart above and decides: "Next time a share moves sideways under a high, I buy. It always breaks out."
Scrolling further back on the same chart shows something else:
- Three months earlier, a similar sideways phase broke lower and fell 4%.
- Six weeks earlier, another one broke higher by 1% and then fell back into the range.
- Two weeks earlier, a third one simply drifted sideways for 15 days.
Only one of the four looked like a clear setup afterwards. The other three were easy to overlook because they did not end in a memorable move. Without written notes from the time, the trader remembers the winner and builds a rule on one example.
Common mistakes
- Studying only the best examples. Look at every case of a pattern, including the failures.
- "I knew it." If you did not write it down before, you cannot be sure you knew.
- Judging a trade by its result alone. A good decision can lose, and a poor one can win.
- Trusting marked-up charts in ads. Perfect entries drawn after the fact prove nothing.
The takeaway
After the outcome is known, it seems obvious. Judge your decisions by what you knew then, not by what you know now.
Check yourself
Quick quiz
4 questions. Instant feedback, nothing is saved.
-
1Tap the candle that, looking back, makes this chart seem easy to read.
Tap the chart.
Once you have seen the breakout candle, the sideways phase looks like an obvious build-up. In real time, it could just as well have broken lower.
-
2What did Baruch Fischhoff's 1975 experiments show?
Participants with outcome knowledge judged it as more likely and were largely unaware of how much that knowledge changed their view.
-
3Why are old charts with marked-up 'perfect' entries misleading?
In hindsight, you pick the examples that fit. In real time, every failed version of the same setup was possible too.
-
4What protects best against hindsight bias in your own trading?
A note written before the outcome cannot be changed by what happened afterwards. Memory can.
of 4 correct.