Nudge vs. Sludge: Why Is the Cancel Button Always So Hard to Find?
I thought I was paying $20 a month. I got charged $240. What sludge is, how it differs from a nudge, and how to use sludge on yourself to break bad habits.
Jae Dokgo8 min read
Nudge vs. Sludge: Why Is the Cancel Button Always So Hard to Find?
Have you ever signed up for something with one click, then had to dig through menu after menu just to cancel?
The sign-up button was big and right in the middle of the screen.
But the cancel button is hidden at the bottom of "Manage Account," inside a settings page, inside another settings page, in tiny print.
When you finally find it and click, you get "Are you sure you want to leave?" and "You'll lose your benefits if you cancel now," over and over. It's a real hassle.
Eventually you think, "Ugh, I'm busy. I'll just do it later," and close the window.
And next month, you get charged again.
In my last post, I wrote about nudges.
A nudge leaves every option on the table and gently changes the environment to guide what people do.
So what happens when someone uses that same approach in the opposite direction?
1. What is sludge?
In 2018, Richard Thaler, co-author of Nudge, published a short piece in the journal Science. It was titled "Nudge, not sludge."[1]
Sludge literally means thick mud or gunk.
In behavioral science, sludge means friction that's deliberately built in to make it harder for people to do things that are good for them.
Put simply:
- Nudge: makes good things easier to do
- Sludge: makes good things harder to do
Thaler's co-author, Cass Sunstein, went on to write an entire book on the subject, called Sludge. It shows how piles of paperwork, long wait times, and complicated procedures are everywhere in our lives, wearing people down until they give up.[2]
In apps and on websites, this kind of design is often called a "dark pattern."
2. Nudge vs. sludge: what's the difference?
Both are design. They just push in completely opposite directions.
| Situation | Nudge (good design) | Sludge (bad design) |
|---|---|---|
| Subscriptions | Canceling is as easy as signing up | One click to sign up, cancel buried deep in the menus |
| Free trials | A reminder before you're charged | Auto-charged with no warning |
| Deleting your account | Delete it right in the app | Have to call customer service to delete it |
| Refunds and claims | Only the paperwork that's truly needed | Ask for so many documents that people give up |
| Retirement savings | Automatically enrolled in the 401(k), free to opt out | Have to fill out separate forms to enroll |
The last row is one of the most famous nudge examples, featured in Nudge.
When one U.S. company switched its 401(k) plan from "opt in if you want to" to "you're enrolled by default, opt out if you want to," participation jumped dramatically.
The options were exactly the same. Only the default changed.[3]
3. One question that separates a good nudge from a bad one
So how do you tell the difference? I think one question is all you need.
"Who does this design actually help?"
If it makes it easier for people to do what they already wanted to do, or what's good for them, it's a nudge.
If it pushes people in a direction that's good for the company but costs them, it's sludge.
Not long ago, I signed up for a paid subscription on a website so I could download images and audio for my content.
I won't name the site. But when I went to pay, the price clearly said $20 a month, so I paid. It turned out that $20 was the monthly rate only if you paid for a full year up front, $240 at once. The regular month-to-month plan was actually $30, and the button for it was tiny and tucked away in a corner.
It clearly said "monthly payment: $20," so my plan was to pay $20 for this month, try it out, and then decide whether to keep it. Then I approved the charge on my card and saw $240 instead of $20. I was shocked. I emailed the site to explain it was a mistake and asked for a refund. The only reply I got was a statement saying payment mistakes weren't their responsibility and no refund was possible. After a lot of back-and-forth, I finally got them to switch me to a monthly plan and refund the other 11 months. But it was not an easy process, and I remember being furious at how deliberately their sludge UX was designed.
That experience shaped the standard I set for myself when designing MOAVO Habits:
Show the price clearly. Make canceling as easy as signing up. Never leave users confused about what they're paying for.
4. What I ask myself as someone who builds an app
But here's the thing: once you're actually building and running an app, the pull toward sludge gets a lot stronger.
There are plenty of ways to get people to use an app longer and more often. Send more notifications. Make people feel worse when they break a streak. Hide the cancel button a little deeper. Your numbers will probably go up.
But what matters is that people aren't staying because they want to. They're staying because it's hard to leave.
So as I keep building MOAVO Habits, I keep coming back to these questions:
- Notifications: Am I only sending reminders for the habits users chose, at the times they chose?
- Streaks: Do the growing dots motivate people, or just leave them feeling guilty when a streak breaks?
- Going paid: Am I being honest about the difference between the free and paid versions?
To be honest, I haven't figured out all the answers yet.
But personally, I believe that just by continuing to ask, "Is this helping users do what they actually set out to do?", MOAVO Habits can at least avoid sliding toward sludge.
5. Use nudges and sludge in reverse on your own habits
Here's the fun part.
Sludge is bad design, but when you use it on yourself, it can become a great tool.
- For habits you want to build, add a nudge to make them easier.
- For habits you want to break, add sludge on purpose to make them harder.
James Clear, one of the world's best-known writers on habits, makes the same point in Atomic Habits: make good habits easy and bad habits hard.
| Goal | What to add | Example |
|---|---|---|
| Work out in the morning | Nudge (make it easier) | Lay out your workout clothes and sneakers next to your bed the night before |
| Read in the evening | Nudge (make it easier) | Leave the book you're reading open on the table |
| Less phone time before bed | Sludge (make it harder) | Charge your phone outside the bedroom |
| Fewer impulse buys on shopping apps | Sludge (make it harder) | Delete the cards saved in your one-click checkout |
| Less late-night snacking | Sludge (make it harder) | Stop keeping snacks at home, so you'd have to go out to the store |
Pick just one and try it for a few days. Then write a quick note about it.
Later, you'll probably find entries like these:
"Charged my phone in the living room, and I didn't reach for it in bed out of habit."
"Typing in my card number every time was such a hassle that I just left things in my cart. The next day, I realized I didn't need them."
As these notes add up, you'll start to see which nudges and which sludge actually work in your life.
6. Once you can spot nudges and sludge
Once you know about nudges and sludge,
everyday life starts to look a little different.
- The path you walk through the grocery store every week
- Where the buttons sit in the apps you use every day
- Free trial screens and cancel buttons
When you're in front of one of them, ask yourself:
"Is this design helping me, or holding on to me?"
Then turn that question around on your own life.
Add more nudges that help you,
clear out the sludge that holds you back,
and lay down your own sludge in front of the bad habits you want to break.
MOAVO Habits is an AI habit journal I built so you can quickly log small experiments like these and their results, and look back on them later.
But a paper notebook or a notes app is a fine place to start, too.
Right now, add one nudge or one bit of sludge to your life.
Then write one line about how it changed what you did.
Download on the App Store · Get it on Google Play
References
- Richard H. Thaler, "Nudge, not sludge," Science 361(6401), 2018. https://www.science.org/doi/10.1126/science.aau9241
- Cass R. Sunstein, Sludge: What Stops Us from Getting Things Done and What to Do About It, MIT Press, 2021.
- Brigitte C. Madrian & Dennis F. Shea, "The Power of Suggestion: Inertia in 401(k) Participation and Savings Behavior," Quarterly Journal of Economics 116(4), 2001.
