Endowment Effect Examples: 5 Places Ownership Quietly Doubles What You Think Things Are Worth
In a Cornell classroom in 1990, half the students were handed a $6 coffee mug and the other half were handed nothing. When both groups…
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Ostrich Effect Investing: What Eleven Months of Not Looking Actually Costs
Researchers with access to 1.2 million Vanguard accounts found something uncomfortable: the day after the Dow falls, the number of investors who log in to…
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Recency Bias Investing: Why “What’s Working Now” Is the Worst Signal You Can Follow
Between January 2016 and December 2025, U.S. mutual funds and ETFs returned 9.9% a year. The average dollar actually invested in those same funds earned…
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Sunk Cost Fallacy Personal Finance Decisions: A $6,300 Case Study in Letting Go
In 1985, two psychologists asked people to imagine they were an airline president who had already sunk $9 million into a plane a competitor had…
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Present Bias and Retirement Contributions: Why “Just Save More” Almost Never Works
In a study of one mid-sized manufacturing company, workers who were asked to commit to saving more later raised their average savings rate from 3.5%…
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The Diderot Effect: Why “Buy It Once, Buy It Right” Quietly Costs More
In 1769, Denis Diderot was given a scarlet dressing gown. Within a year he had replaced his desk, his chair, his prints, his bookshelves, and…
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No Spend Challenge Rules: Why the 30-Day Version Fails and What to Do Instead
The median time it takes a new behavior to become automatic is 66 days. A 30-day no spend challenge ends at day 30. That gap…
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The Planning Fallacy in Personal Finance: Why a $30,000 Kitchen Closes at $41,000
Thirty-seven psychology students were asked how long their senior thesis would take. Their average estimate was 33.9 days. The average actual completion time was 55.5…
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Does Paying With Cash Make You Spend Less? What 392 Studies Actually Found
In 2001, two MIT researchers ran an auction for Boston Celtics tickets and found that bidders told to pay by credit card bid roughly twice…
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Framing Effect Pricing Psychology: Why Knowing About It Doesn’t Protect Your Wallet (2026)
In 1981, two psychologists handed 307 people a choice between two public health programs. The programs were mathematically identical. Depending on which set of sentences…
