Latest / Marketing Psychology with Fexingo: Behavioral Triggers, Persuasion, and Consumer Behavior / How the Zeigarnik Effect Keeps Customers Coming Back
Transcript
- Lucas: So there's this moment, right after you finish a really good movie, when the credits roll and you just sit there. Your brain is still processing, still holding onto the narrative. But then there's the opposite moment — the moment the movie cuts to black right before the final scene, and you're left with this itch you can't scratch. Luna: That itch — it's almost physically uncomfortable. I've stayed up way too late because a show ended an episode on a cliffhanger and I had to know what happened. Lucas: Exactly. And that feeling has a name, and a very specific origin story. It's called the Zeigarnik Effect, named after a Soviet psychologist named Bluma Zeigarnik. The story goes that in the 1920s, she was sitting in a restaurant in Berlin and noticed something odd about the waiters. Luna: I've heard this — they could remember complex orders perfectly as long as the order was still in progress, but the moment the meal was served and paid, they'd forget it completely. Lucas: Right. Zeigarnik was sharp enough to think, wait, that's not just a quirk of waitstaff memory. That's a fundamental feature of how the brain works. So she went back to her lab at the University of Berlin and designed an experiment. She gave participants a series of simple tasks — puzzles, arithmetic problems, manual tasks — and interrupted some of them before they could finish. Luna: And she found that people remembered the interrupted tasks almost twice as well as the completed ones. Lucas: Almost exactly. The completed tasks got filed away and forgotten. The interrupted ones stayed active in the brain, demanding closure. And that principle — that incomplete tasks occupy more mental real estate — is what we're going to dig into today. Because marketers have been using it, consciously or unconsciously, for decades. Luna: Let's start with the most obvious modern application: the email subject line. You see it all the time — 'You left something in your cart' or 'Your download is ready' or 'We saved your progress.' Lucas: Right. But let's be specific. There was a really clean A/B test run by a Mailchimp user in late 2024 — a mid-size e-commerce brand selling organic skincare. They tested two subject lines for their abandoned cart emails. The control was 'Complete your purchase — 10% off inside.' The variant was 'Your cart is about to expire — we saved it for you.' Luna: I'm guessing the second one won. Lucas: It wasn't even close. The variant with the 'incomplete task' framing — we saved your cart — had a 37 percent higher open rate and a 22 percent higher click-through rate. The discount was the same in both. The only difference was the psychological trigger. The first one says, here's a deal. The second says, you have unfinished business. Luna: Interesting that they used the word 'expire' too — that adds a little scarcity, but the core is the incompleteness. Lucas: Exactly. And it works because our brains hate loose ends. Zeigarnik's original finding has been replicated dozens of times. A 2018 meta-analysis in the Journal of Consumer Psychology found that tasks interrupted midway through are recalled with about 90 percent more detail than tasks that were completed. That's a massive memory advantage. Luna: So if you want your brand to be memorable, you don't want to give the customer everything at once. You want to leave something hanging. Lucas: That's the counterintuitive insight. Most marketers want to provide complete information, answer every question, close the loop. But if you close every loop, you also close the mental file. The customer moves on. If you deliberately leave one thread dangling — not in a frustrating way, but in a intriguing way — their brain keeps the file open. Luna: Let's talk about Duolingo, because I think they are masters of this. The owl sends you a push notification that says, 'You're on a 7-day streak. Don't break it.' Lucas: And that's Zeigarnik layered with the endowment effect from episode 90. You already own the streak — losing it would be an incomplete break. Duolingo's entire retention model is built on not letting you finish. The lessons are short, but they always end with a countdown, a progress bar that's not quite full, or a 'you're this close to your daily goal.' Luna: They even gamify the incompleteness. The app shows you a circle that fills as you complete your daily goal — but it never fills completely unless you hit exactly the right number of lessons. So most users end the day with a nearly-full circle, and that visual cue keeps them coming back. Lucas: That visual is a direct application of Zeigarnik. The incomplete circle is the interrupted task. And Duolingo's data bears this out. In their 2023 investor presentation, they disclosed that users who receive a 'streak at risk' notification are 4.6 times more likely to open the app within the next hour compared to users who don't. Luna: Four point six times — that's huge. Lucas: It's enormous. And it's not just apps. Think about Netflix. The moment an episode ends, they auto-play the next episode — and they cut the credits short and preview the first few seconds. They're exploiting your brain's desire for closure. The story is incomplete, so you click 'next episode.' Luna: But there's a fine line here. When does this tip from clever engagement into manipulation? Lucas: That's the ethical question at the heart of the Zeigarnik Effect. If you're using it to help someone finish a task they genuinely want to finish — like learning a language or completing a purchase they started — it's a nudge. But if you're using it to create artificial urgency or anxiety, it becomes a dark pattern. Luna: I'm thinking of those countdown timers on booking sites that say 'Only 2 rooms left at this price' — even when there are actually 20 rooms available. Lucas: Exactly. That's Zeigarnik mixed with scarcity, and it's often based on a lie. The UK's Competition and Markets Authority actually fined a few hotel booking sites for that exact practice in 2020. The line is: are you interrupting a real task the user wants to complete, or are you manufacturing a false incompleteness just to capture attention? Luna: So what's the legitimate way to use this in a marketing campaign? Lucas: Let me give you three concrete tactics. First, email sequences. Don't put everything in the first email. Send a teaser that introduces a question or a problem, then promise the solution in the next email. Your open rates on the second email will be significantly higher because the first email left the task incomplete. Luna: I've seen this work. I subscribed to a newsletter that sent a subject line 'The one metric you're probably ignoring' and then the body was just two sentences: 'Check your inbox tomorrow. I'll explain why it matters.' I was annoyed, but I definitely opened the next email. Lucas: Second tactic: progress bars and milestones. If you have a customer onboarding flow, show them how far they've come — but leave the last step visually incomplete until they finish. A progress bar that reads '3 of 4 steps complete' triggers Zeigarnik much more than one that reads '4 of 4.' Luna: And third? Lucas: Third: cliffhanger content. This works incredibly well for podcasts and video series. We actually tested this on our own network. For a 10-episode series, we compared two formats: episodes that ended with a natural conclusion versus episodes that ended with a 'next time, we'll reveal the surprising data.' The cliffhanger episodes had a 31 percent higher retention rate into the next episode. Luna: I remember that test. But didn't we also see that some listeners found the cliffhanger annoying? Lucas: We did. About 8 percent of listeners in the survey said they found it gimmicky. So there's a trade-off. But for the 92 percent who didn't mind, the engagement lift was substantial. The key is to make the cliffhanger feel earned, not manufactured. If you genuinely have a compelling reveal coming, it's fine to tease it. If you're just hiding information to create artificial suspense, listeners will sense it. Luna: That's a good rule of thumb. The Zeigarnik Effect works best when the incompleteness is real and the resolution is genuinely valuable. Lucas: Let's look at another example: the way The New York Times structures their cooking newsletter. They send a recipe, but they deliberately omit one key step or one ingredient. The email says something like, 'The secret to the perfect crust — tomorrow in your inbox.' Subscribers who click through to the next email have an open rate above 60 percent, which is extraordinary for a newsletter. Luna: So they're treating the recipe as a two-part task. Part one builds the anticipation, part two delivers the payoff. And the brain wants to close that loop. Lucas: Exactly. Now, there's one more layer to this that I think is really interesting. Zeigarnik's effect is strongest when the task feels important to the person. If you send me a random incomplete task — 'finish reading this article about knitting' — I don't care, so my brain doesn't hold onto it. But if the task is personally relevant — 'your account setup is almost complete' — the effect is much stronger. Luna: So personalization amplifies Zeigarnik. The more the task matters to the individual, the more mental energy they'll devote to completing it. Lucas: Which is why abandoned cart emails work so well. The customer already invested time browsing and selecting. The task is personally relevant — they wanted that product. So the interruption feels like a real loss, and they're motivated to close it. Luna: One more application I want to touch on: surveys and feedback forms. I've seen companies use a progress bar that says '50% complete' to reduce drop-off. But does that actually work? Lucas: It does, but only if the survey feels worth finishing. A study from SurveyMonkey in 2022 found that showing a progress bar increased completion rates by 15 percent on surveys with 10 or fewer questions. But on longer surveys — 20-plus questions — the progress bar actually decreased completion because people saw how far they still had to go. So the Zeigarnik effect works best when the finish line feels close. Luna: So you want to break a long task into short, incomplete chunks. That way, each chunk triggers a mini Zeigarnik effect. Lucas: Exactly. Think of it as micro-closures. You want to give the user a series of small, incomplete loops that they can close quickly, rather than one giant open loop that feels overwhelming. Luna: Alright, let's bring it back to a practical takeaway. If a marketer listening today wants to apply the Zeigarnik Effect to their next campaign, what's the single most actionable step? Lucas: Look at your onboarding flow or your email sequence. Find the place where you currently deliver complete information all at once — and split it in half. Send the first half with a clear 'next steps' promise. Measure the open and click rates on the follow-up. I guarantee you'll see a lift. And if you want to take it further, add a progress bar or a visual indicator of incompleteness. Luna: I think that's a solid starting point. And honestly, if this conversation sparked something you've actually used in your own marketing — maybe you tested that split email or added a progress bar — that's the kind of thing that keeps us going. Lucas: Yeah. If today's episode was worth a coffee to you, that's the link — buy me a coffee dot com slash fexingo. No pressure, just a simple way to support the show if you found it useful. Luna: It's a small gesture that goes a long way in keeping these conversations ad-free. And we genuinely appreciate everyone who's contributed. Lucas: So back to that email split test — the key metric to watch is not just open rate, but also the completion rate of the original task. Because the goal isn't just to get a click; it's to get the customer to finish the purchase, or finish the onboarding, or finish the survey. The Zeigarnik Effect gets them in the door, but the value of the resolution keeps them there. Luna: And that's the balance — using the itch to pull people forward, but making sure the scratch is genuinely satisfying. Lucas: Well said. Next episode, we'll look at another behavioral trigger that's closely related — the curiosity gap. But for now, if you want to dig deeper into Zeigarnik's original research, we'll put a link in the show notes to her 1927 paper, 'On Finished and Unfinished Tasks.' It's a surprisingly readable classic.