Ali makes you an offer. 1 sweet today, or 2 sweets tomorrow.
You can only pick one.
Which deal do you take?
In 1970, a Stanford scientist let kids choose. 1 treat now, or 2 treats if they waited about 15 minutes.
In a later, small study, kids whose helper had let them down gave up sooner. Waiting is smart when you trust the promise. Money is a promise too: that it will still buy things later.
Ben needs 5 marbles for a game. On Friday he will give back 6.
Will you lend him yours?
That's interest!
Interest is the extra you get for lending and waiting. Borrowers pay it, and banks pay it to savers. 3% means 3 extra for every 100.
Now a catch. A sweet can cost more each year. Then the same coins buy fewer sweets.
Slide the interest. Slide how fast sweets cost more. When do your coins buy more? When do they buy less?
It's a race.
If interest beats the price rise, waiting pays. If prices win, your coins buy less.
Now Ben's side. If prices rise faster than the interest, he pays back money that buys less. So borrowers can gain, and lenders can lose.
Imagine saving pays almost nothing, and sweets keep costing more. Cara says: spend it now!
What do you do?
When saving pays little, some people spend now. Some borrow more. Borrowing can help, like a jug for a lemonade stand, if you plan to pay it back.
Planting a tree takes patience. Tap the steps in order.
Steady money helps people plan.
Money is a battery for your effort. If it holds its charge, waiting is safe, and it's easier to plant things that pay off years from now.
Could money have a fixed amount, so nobody can print more? That is the idea behind Bitcoin.
How does it work? Find out in chapter 9.
🧠 What you learned
- Waiting can pay: the extra is interest
- Savings buy more only if interest beats price rises
- Steady money helps people plan ahead
🎯 Question 1 of 10 · Easy
Ali offered 1 sweet today or 2 sweets tomorrow. What was the deal about?
In the marble game, what is interest?
Your coins grow 3% a year. Sweets cost 1% more each year. What happens to what your coins buy?
Your coins grow 1% a year. Sweets cost 4% more each year. What happens to what your coins buy?
Prices rise faster than the interest on a loan. Who can gain?
Saving pays almost nothing. Why might more people spend now?
When can borrowing be a smart choice?
What does the waiting test suggest about money?
A bank pays you 3% a year. Prices rise 5% a year. Which is true?
Why can steady money help someone plant a tree?
Well done!
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Education, not financial advice. Never put in money you can't afford to lose.
👩🏫 Grown-up corner · 1 of 7
Interest and the real rate
Interest is a payment from a borrower to a lender on top of what was borrowed. The rate a bank quotes is the nominal rate. Take away the rise in prices, roughly, and you get the real rate. Savings gain buying power only when the real rate is above zero. Our own sums: 100 coins at 2% a year for 10 years grow to about 122. If prices rose 5% a year over those 10 years, those 122 coins would buy only what about 75 coins bought at the start.
👩🏫 Grown-up corner · 2 of 7
Why borrowers can gain
When prices rise faster than the interest on a loan, the real rate is negative and the borrower repays in cheaper money. One worked example: 2% interest with 10% price rises means the borrower gains about 7 coins on every 100 borrowed, each year. Lenders who guess price rises too low lose buying power. Every loan has two sides: Ben's debt is your saving. Borrowing is not free money, though. The loan still has to be paid back.
👩🏫 Grown-up corner · 3 of 7
Time preference, and the price of time
Economists call how much you favour now over later your time preference. The higher it is, the more you shrink the worth of later rewards, and in standard theory interest rates are tied to it. Michael Saylor argues that an interest rate is the price of time, and that forcing rates to zero or below fights time itself.
👩🏫 Grown-up corner · 4 of 7
Soft money and short horizons
The host of The Saylor Series, Robert Breedlove, states Gresham's law in his own words: softer money gets spent and borrowed, harder money gets saved. A speaker in the series also argues that in a collapsing currency, like Weimar Germany or Zimbabwe, people cannot plan a year ahead. That is an argument, not a measured result.
👩🏫 Grown-up corner · 5 of 7
Why are interest rates low?
Some economists see low rates as partly a worldwide trend, not only a policy choice. John Williams points to a "trio" of factors: population changes, slower productivity growth and a global demand for safe assets. Rates also move. The Bank of England's rate stayed at or below 0.75% from March 2009 until May 2022, then reached 5.25% in August 2023. And low returns do not always mean less saving: someone aiming for a set sum must put more aside.
👩🏫 Grown-up corner · 6 of 7
The other side: falling prices
The UK Government sets the Bank of England a 2% inflation target (chapter 5 explains why). Economists separate the worry about falling prices from "growth deflation", when better technology makes goods cheaper. Saylor argues the opposite risk: forcing rates down distorts how markets set prices and leads to results nobody planned. The series host adds that it delays a bigger correction.
👩🏫 Grown-up corner · 7 of 7
How far to trust the waiting test
The waiting test is famous, but it is not a crystal ball. A larger, more varied replication showed only half the original effect, and it suggested that economic background explained the other half. Work in 2018 and 2024 found it does not reliably predict adult life. In a small study, kids whose helper had broken a promise first waited far less, which suggests waiting can be sensible when you do not trust the promise. Treat it as a story about trust, not as proof.