TOO BAD THERE WAS NO BRITISH HOPKINS:

So, how did Hopkins start America brushing?

By taking advantage of a quirk in the neurology of habits. It wouldn't be until almost a century later that medical schools and psychology labs would fully understand why habits exist and how they function. Today, we can create and change habits almost like flipping a switch.

But there are historical outliers who seemed to intuitc or accidentally stumble into - these insights before anyone else. Hopkins created a toothbrushing habit by identifying a simple and obvious cue, delivering a clear reward and --most important --by creating a neurological craving.

And craving, it turns out, is what powers a habit.

When Hopkins signed on to promote Pepsodent, he realized he needed to find a trigger for its daily use. He sat down with a pile of dental textbooks. "It was dry reading," he later wrote in his autobiography. "But in the middle of one book I found a reference to the mucin plaques on teeth, which I afterward called 'the film.'

"That gave me an appealing idea. I resolved to advertise this toothpaste as a creator of beauty."

Soon, cities were plastered with Pepsodent ads. "Just run your tongue across your teeth," read one. "You'll feel a film--that's what makes your teeth look 'off color' and invites decay."

"Note how many pretty teeth are seen everywhere," read another. "Millions are using a new method of teeth cleansing. Why would any woman have dingy film on her teeth? Pepsodent removes the film!"

All habits--no matter how large or small--have three components, according to neurological studies. There's a cue--a trigger for a particular behavior; a routine, which is the behavior itself; and a reward, which is how your brain decides whether to remember a habit for the future. When Hopkins identified tooth film, he found a cue that had existed for eons. Moreover, the reward that Hopkins was promising was hard to resist. Who doesn't want a prettier smile? Particularly when all it takes is a quick brush with Pepsodent?

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