Concept
The decision journal
A decision journal is one page per consequential decision, written before the outcome: the options widened, the assumption tested, a numeric probability, the friend's advice, a premortem and a tripwire date. It is the road's synthesis and the only record memory cannot rewrite.
Duke and the Heaths arrive at the same place from different directions: the only way to improve at decisions is to make them visible to yourself at the time and afterwards. Memory rewrites every decision into a story in which you knew then what you know now. The journal defends against that with six questions. What is the decision, with at least three options. What assumption am I betting on and how did I test it. What is my probability that it works out, and what does that mean specifically. What would I tell my best friend. It is a year later and it failed; why. On what date or number will I review. Four or five entries a month is plenty; read together, they show patterns no single decision can.
A real-life example
After a month a manager has five entries: a job, a flat, a hire, whether to report a colleague's mistake, and a loan to a cousin. Read together they show one pattern already: his probabilities are honest at work and ten points too kind with family.
How to use it
- 1One page, six questions, written before the outcome is known.
- 2Put the review date in your calendar as you write the entry.
- 3At the end of each month, read all entries together and look for the villain you keep letting in.