In 1927, a psychology student noticed something unremarkable in a Vienna café. Waiters could recall unpaid tabs with perfect detail. Completed orders vanished from memory almost immediately.

That observation — that unfinished business stays active in working memory while finished business gets filed away — became one of the most documented effects in psychology. Bluma Zeigarnik published her findings. The effect carries her name. And the advertising industry has been applying it, knowingly or not, ever since.

Netflix did not invent the cliffhanger. But they refined it to a science. The autoplay feature, the end-of-episode preview, the season finale that resolves nothing — each is a deliberate application of the same principle. The brain that encounters an open loop allocates cognitive resource to resolving it. Closing the laptop requires more willpower when something is unfinished.

The average marketing funnel is designed around completion. Move the prospect from awareness to consideration to decision. Close the loop. Get the sale.

What the Zeigarnik Effect suggests is that the best funnels do not close loops — they open them. Each stage introduces something unresolved that the next stage addresses. The prospect who reads your content is left with a question. The email they receive the following day answers it — and opens a new one. The sales page reveals the method without revealing the transformation, and the product purchase completes the narrative.

This is not manipulation. It is the same structure that makes any story worth reading. The reader who reaches the last page because they needed to know what happened is not being tricked. They are following an instinct the human brain has always had.

Email sequences. The most effective email sequences are serialised, not standalone. Each message closes one open loop and introduces another. Day one names a problem. Day two reveals a counter-intuitive aspect of it. Day three begins to explain a solution. Day four finishes it — mostly — and hints at what comes next. The subscriber who stays engaged through this sequence is the one who will buy when the offer arrives.

Content marketing. A series of connected articles dramatically outperforms the same volume of unconnected ones. The reader who finishes part one and knows part two exists will return. The reader who finishes a standalone piece has no reason to.

Sales pages. Open loops on a sales page are not buried at the bottom. They run through the entire narrative. Name the problem early. Introduce the mechanism. Explain why the usual solutions fall short. Reveal the product as the resolution of everything that came before.

There is a productivity application here too. Ron Friedman's research on completion effects shows that people are motivated by a sense of progress toward an unfinished goal more than by the prospect of a reward at the end. This is why progress indicators on checkout pages reduce abandonment. It is why limited-time offers work better when the countdown is visible. The open loop creates urgency that no amount of benefit-listing achieves.

The Zeigarnik Effect is not a trick. It is an accurate description of how human attention works. Marketers who understand it structure their content differently — not around resolution, but around the strategic placement of questions that the next piece will answer. The audience that is waiting for part two is the audience that is paying attention.