O.J. Simpson was one of the most famous sportsmen in America.

But in 1994 the police charged him with hacking his wife and her lover to death.

Simpson went on the run in a Ford Bronco.

He was followed by dozens of police cars and news helicopters.

95 million people watched the two-hour chase, live on TV.

Meanwhile, attorney Robert Kardashian read out Simpson’s prepared suicide note.

Simpson didn’t die, but it all seemed a confession of guilt, an open and shut case.

And later, in court, the evidence was overwhelming.

But the defence had one straw to grasp at.

A glove, which the police said the murderer wore, appeared too small for Simpson.

Johnny Cochrane, Simpson’s lawyer, managed to build this into an argument.

He got it to stick in the jury’s mind above all the other evidence.

He did it by making up the line: “If the glove don’t fit you must acquit.”

And every time another piece of prosecution evidence was raised, the answer was simply: “If the glove don’t fit you must acquit.”

Because of the way it was phrased, it seemed to distil all the complicated legal arguments down to a single point.

And, despite all the evidence against him, O.J. Simpson was found not guilty.

The power of logic, delivered in rhyme, persuaded the jury.

This is a cognitive bias known as the “Rhyme-as-reason effect”.

A saying is more truthful and memorable when it’s delivered in rhyme.

Mathew McGlone proved this in a paper at the Dept. of Psychology at Lafayette College.

Many more respondents remembered the line: “What sobriety conceals, alcohol reveals” than remembered the line: “What sobriety conceals, alcohol unmasks”.

It seems obvious to us, so we may wonder why more advertising doesn’t use it.

After all, it’s something advertising used to do well.

One of the most successful public health campaigns ever, was a poster about covering your mouth: “Coughs and Sneezes Spread Diseases”.

One of the most successful road safety campaigns, was about keeping your distance: “Only a fool breaks the two-second rule”.

A campaign that saved countless lives was for seat belts: “Clunk, Click, every trip”.

Another campaign hijacked an entire market, and was responsible for selling over 20 million cans a year: “Beanz Meanz Heinz”,

In the 1920s, ad agency Mather & Crowther built a fruit into a health food with the line: “An apple a day keeps the doctor away”.

(Many people still think that’s age-old wisdom, handed down over generations.)

The same agency made milk a staple with the line: “Drinka Pinta Milka Day”.

And rhyming logic dominated the holiday market: “Don’t just book it, Thomas Cook it”.

It also made a chocolate bar into an energy food: “A Mars a day helps you work, rest, and play”.

Not only is rhyming logic more believable, it’s also more repeatable.

The wartime propaganda campaign to make secrecy essential caught on across the English-speaking world with the line: “Loose lips sinks ships”.

Even the phrase you’ll hear repeated today, all over Essex every June: “No carbs before Marbs”.

The learning is that rhyming logic makes a statement seem unarguably sensible.

Wouldn’t you have thought that was a good thing for advertising to do?

When you want to change someone’s mind, when you want it to stick in their head, when you want it to get it passed on.

What we now call going viral.


We know it works, I wonder why people are so embarrassed to use it.