The simple riddle that 50% of Harvard students get wrong

More than 50% of Harvard students got this question wrong: A bat and a ball cost $1.10 total, and the bat costs one dollar more than the ball.

Most people's initial instinct is to answer ten cents.

The correct answer is five cents. This is the first question in the Cognitive Reflection Test.

The test was designed by Professor Shane Frederick from Yale University to measure how well people can suppress their initial reaction in favor of a more thoughtful answer.

A simple test with only three questions designed to measure cognitive reflection ability.

• When given to 3,500 people (mostly college students), only 17% could get all three questions correct • Performance on this test correlates with SAT scores • Worse performance on the test correlates with increased susceptibility to cognitive biases

For only three questions, the test is a surprisingly revealing measure of cognitive ability and bias susceptibility.

The worse you perform on this test, the more prone you are to cognitive biases.

When questions are presented in a harder to read font, 65% of people get all three questions correct, compared to the typical 17%.

This represents a staggering improvement of nearly 50 percentage points just by changing the font difficulty.

The effect of harder to read fonts shows up in a variety of other circumstances beyond the riddle test.

Harder to read fonts also improve memory and learning in educational settings.

In a public school in Ohio, researchers asked teachers to change fonts in worksheets and PowerPoint presentations from standard fonts like Times New Roman or Arial to harder to read fonts like Monotype Corsiva.

One would expect that harder to read fonts would hinder the learning process.

Students exposed to the harder to read fonts scored significantly higher on their later tests compared to classes using normal fonts.

The seemingly negative change in readability actually produced a positive effect on student performance.

• System 1: Quick, intuitive, and effortless thinking that helps with instant recognition and simple calculations • System 2: Slow, analytical, and effortful thinking that kicks in when concentrating on problems

Most of the time, our brains operate on System 1 thinking.

Our brain switches to System 2 thinking when it encounters cognitive strain, meaning something is hard to process.

• System 1 responds instantly with '10 cents' (the wrong answer) • System 2 provides '5 cents' (the correct answer) after careful deliberation

When something is hard to process, your brain switches to a more deliberate type of thinking.

Using a harder to read font is one way to increase cognitive strain and trigger more careful thinking.

• For the riddle test: harder fonts make people think more carefully and get the right answer • For learning: harder fonts induce deeper processing of information, leading to better understanding

People normally fail the cognitive reflection test because they're operating on automatic System 1 thinking without cognitive strain.

When researchers present a statement like 'Adolf Hitler was born in 1892' in a more readable font, participants rate it as more truthful and believe it comes from a more expert source.

Without cognitive strain, we are less likely to question statements, making us more susceptible to believing false information.

Easy-to-read fonts can be used to fool people into accepting statements without critical evaluation.

Understanding this effect helps us recognize when we might be manipulated through presentation design.

When proofreading a resume or essay, change the font size and style to a harder to read one, which increases cognitive strain and helps you spot typos you would normally miss.

• Familiar words are normally processed automatically by System 1, causing typos to be missed • Harder to read fonts force System 2 thinking, allowing better error detection

By increasing cognitive strain, you engage more of your System 2 thinking, which is better at careful, detailed analysis.

Deliberately making text harder to read can actually improve your ability to catch mistakes and learn material more deeply.