You start a small home project. You guess it takes one weekend. How long do projects like it usually take?
Your brain is good at many things. Guessing the future is not one of them. It tends to think plans will go fast, cost little, and go smoothly.
Researchers call this the planning fallacy. We see it again and again.
planning fallacy
Our habit of guessing a plan will go better than it does. We expect less time, money and risk.
Sources
Daniel Kahneman, Thinking, Fast and Slow
Annie Duke, Thinking in Bets (2018)
Jeff Bezos, 2015 letter to Amazon shareholders
Gary Klein, Harvard Business Review (2007)
Econlib, “Opportunity Cost”
Danziger, Levav & Avnaim-Pesso, "Extraneous factors in judicial decisions", PNAS 108(17), 2011 — https://doi.org/10.1073/pnas.1018033108 (the ~65% → near-zero parole figures the module reports; the study is described but its authors are never named)
Weinshall-Margel & Shapard, "Overlooked factors in the analysis of parole decisions", PNAS 108(42), 2011 — https://doi.org/10.1073/pnas.1110910108 (case ordering was not random; supports the module's existing hedge and the fix at index 36)
Iyengar & Lepper, "When choice is demotivating: Can one desire too much of a good thing?", Journal of Personality and Social Psychology 79(6), 995–1006, 2000 — https://doi.org/10.1037/0022-3514.79.6.995 (Draeger's Grocery, Menlo Park; 24 vs 6 Wilkin & Sons jams; 3% vs nearly 30% purchase — read in full, numbers confirmed)
Scheibehenne, Greifeneder & Todd, "Can there ever be too many options? A meta-analytic review of choice overload", Journal of Consumer Research 37(3), 409–425, 2010 — https://doi.org/10.1086/651235 (63 conditions, 50 experiments, N=5,036, mean effect size near zero — the replication caveat)
Arkes & Blumer, "The psychology of sunk cost", Organizational Behavior and Human Decision Processes 35(1), 124–140, 1985 — https://doi.org/10.1016/0749-5978(85)90049-4 (Ohio University Theater season tickets; the module names the authors but the reference list omits the paper)
Mitchell, Russo & Pennington, "Back to the future: Temporal perspective in the explanation of events", Journal of Behavioral Decision Making 2(1), 25–38, 1989 — https://doi.org/10.1002/bdm.3960020103 (the study behind Klein's 30% prospective-hindsight figure; named in the module, absent from the reference list)
Schwartz, Ward, Monterosso, Lyubomirsky, White & Lehman, "Maximizing versus satisficing: Happiness is a matter of choice", Journal of Personality and Social Psychology 83(5), 1178–1197, 2002 — https://doi.org/10.1037/0022-3514.83.5.1178 (the measurement behind the maximizer claim)
Gary Klein, "The Pre-Mortem Method", Psychology Today, January 2021 — https://www.psychologytoday.com/us/blog/seeing-what-others-dont/202101/the-pre-mortem-method (the ONLY source for the "20-30 minutes" the module states. Verified 2026-08-11 against the licensed HBR Sep2007 text via Business Source Complete: the 2007 article gives NO premortem duration at all. Its only times are "over the next few minutes" for the writing step and a "90-minute kickoff meeting" in an unrelated anecdote — which is where the circulating "90 minutes for a premortem" comes from. A previous pass credited this to Klein's October 2015 "Pro-Mortem Method", a different article about imagining SUCCESS, which also gives no duration.)
Amazon.com, "2015 Letter to Shareholders" (published April 2016) — https://s2.q4cdn.com/299287126/files/doc_financials/annual/2015-Letter-to-Shareholders.PDF (full Type 1 / Type 2 one-way-door passage; read in full, both quotations verified verbatim)
David R. Henderson, "Opportunity Cost", The Concise Encyclopedia of Economics (Econlib) — https://www.econlib.org/library/Enc/OpportunityCost.html (the existing Econlib entry, with its author named; movie/book quotation verified verbatim)
Daniel Kahneman, Thinking, Fast and Slow (2011), ch. 23 — add the year to the existing entry; source of the Seymour Fox curriculum-team passage (about 40% gave up; none finished in under seven years or over ten) and of the verbatim "inside view" quotation
Barry Schwartz, The Paradox of Choice: Why More Is Less (2004) — keep as the popular account, but the measurement is Schwartz et al. 2002 above
Chip Heath & Dan Heath, Decisive: How to Make Better Choices in Life and Work (2013) — source for narrow framing and the four WRAP steps; currently uncited even though the module names both
Suzy Welch, 10-10-10: A Life-Transforming Idea (2009) — source for the 10-10-10 rule and for the "the numbers are not literal" info_pop; currently uncited
Herbert A. Simon, "Rational choice and the structure of the environment", Psychological Review 63(2), 129–138, 1956 — where satisficing was named; confirms the module's "in the 1950s" (cited from standard bibliographic record, not read in full this session)
Read end to end and corrected: August 10, 2026. Numbers checked: August 10, 2026.