You pull out the key to open your house. You unlock the door and get inside. Then several hours later you’re looking for the key and wondering where it is. And you discover that you have left it behind on the door. Has this happened to you?

To understand why it happens, let’s flashback to Bluma Zeigarnik, a Russian psychologist. One evening, Zeigarnik and her friends went out for dinner to a restaurant. They had a lovely meal. Guess what the highlight was? It was the service. More specifically, their waiter. He had an amazing memory. So as everybody placed their orders, he remembered every little detail, without writing anything down. He remembered who ordered what. And how they wanted it. Zeigarnik and her friends were all amazed by the waiter’s memory.

After the meal, they were driving back when Zeigarnik discovered that she had left her jacket behind in the restaurant. So she turned around, drove back to the restaurant and sought out that friendly waiter who she knew would be happy to help her locate her jacket. Imagine her horror though when she found the waiter, but the waiter didn’t even recognize her. What happened?

It got Zeigarnik thinking. And her research then showed how our brain tends to work. When a task is completed, our brain hits the delete button. And our memory gets wiped clean. Our short term memory struggles with space to retain information. So it keeps only the unfinished tasks alive. And the minute a task is completed it hits the delete button. And that’s why waiters at restaurants will remember every little detail of your order. But only until the bill is made. That’s why when we photocopy a document, we pick up the copy and walk away, leaving the original behind. This has come to be known as the Zeigarnik effect. A term that describes how our short-term memory deletes completed tasks. Fascinating, isn’t it?

The Zeigarnik effect might explain why at a bank’s ATM, you are now required to pull your card out before collecting the cash. They know Zeigarnik will be at play and once you collect the cash, the task is finished and good chance you will forget to take your card back.

It’s something we can all put to good use. Look at what Netflix does. You will find through all their serials, every episode ends tantalisingly. That 30-minute episode ends at a point where you will say ‘wow, what happens next’? You want to know, you want to come back. There is no closure at the end of that episode and that’s what brings us back all the time. Had there been closure, chances are we’d quickly forget about it. Maybe a powerful idea for all of us. If there is something you want to make sure remains alive, keep it just a bit unfinished. Writing a book? Make sure you end every writing session at a point of suspense or tension. Don’t resolve it. Don’t finish it. That will bring you back next day to writing again.

The Zeigarnik effect might also explain my favourite piece of communication advice. It’s this. Someone said that there are really two golden rules of communication: 1. Never tell everything at once.

That’s it. Ah, the Zeigarnik effect!

The writer is an author, speaker and leadership coach and former MD of Kimberly Clark Lever