What Failing 15% Of The Time Actually Looks Like

A new study proposes a mathematical formula as the secret to success. We've done the workings-out, so you don't have to.

Having one of those days where everything’s going wrong? Well, shrug it off, because failing 15% of the time is the key to success, according to a study.

Educational scholars have long recognised that in order to learn and grow, people need to fail every once in a while. But the latest study, led by the University of Arizona, proposes a mathematical formula for this.

For optimal learning and progression, tasks need to be hard enough for us to fail 15% of the time, or succeed 85% of the time, the researchers suggest.

So we did the maths. Optimal failure works out to be (more or less) one-seventh. In other words, you’re totally allowed to have one bad day each week – or 1.05 days, to be precise.

And if you’ve just had a year of interview rejections and been overlooked for a promotion, give yourself a break, it’s just a drop in the ocean when you consider the breadth of your whole career.

In fact, if you work from the age of 18 to 65, you can expect seven whole years in your 47-year career to be a disappointment. But don’t worry, because it is, in theory, setting you up for long-term success.

The Arizona researchers, with collaborators at Brown University, the University of California, Los Angeles and Princeton, came up with the so-called “85% Rule” after conducting a series of machine-learning experiments, in which they taught computers simple tasks, such as classifying different patterns into categories. The computers learned fastest in situations where the difficulty was such that they responded with 85% accuracy.

The researchers said the “85% Rule” has previously been monitored in animals and is “likely” to also be relevant to humans. Lead author, Professor Robert Wilson, used the example of a radiologist learning to tell the difference between images of tumours and non-tumours to explain how it works.

“You get better at figuring out there’s a tumour in an image over time, and you need experience and you need examples to get better,” he said. “If I give really easy examples, you get 100% right all the time and there’s nothing left to learn.

“If I give really hard examples, you’ll be 50% correct and still not learning anything new, whereas if I give you something in between, you can be at this sweet spot where you are getting the most information from each particular example.”

Failing never felt so good.