Definition
The default effect is the tendency for people's choices to tilt strongly toward leaving a pre-set option as it is. To change it, you have to weigh what is better and actually do something, and that small effort turns out to be a higher hurdle than you'd think. So what gets set as the default can change the overall outcome.
Why You Never Change Your New Phone's Ringtone
When you turn on a new phone, the ringtone and wallpaper are already set. You didn't pick them because you loved them, yet months later they're often still there. Maybe you've even been in a classroom where a ringtone went off and several people dug into their bags at the same time.
It's not that changing it is hard. You open settings, scan the list, listen to a few, and decide. Done. But at every step of that short process, a thought sneaks in: "Do I really need to do this right now?"
Even picking one option takes time and attention. The more things you have to decide in a day, the less of that you have left. So we often end up choosing to leave whatever is already set as it is.
Even in Bigger Choices Than Ringtones
The same force shows up in far more important places than ringtones. When you sign up for an app, if the box agreeing to receive ads is already checked, many people just move on to the next screen that way. That's why the Court of Justice of the European Union ruled in 2019 that consent given through a pre-checked box is not valid consent.
Autoplay of the next episode in a video app works the same way. If it's on by default, few people turn it off. If it's off by default, few people turn it on. People's tastes didn't change. Only the starting point did.
There's also a well-known study of a US company that switched new employees to being enrolled in the retirement plan by default. Far more people ended up enrolled than back when they had to sign up on their own. Same people, same conditions, but one starting point changed the result.
Part of it is that a default can read as a signal: "this is what people usually do." We trust that whoever set it up wouldn't have picked something strange.
To Be a Little More Precise
Plenty of people do end up changing their ringtone to suit their own taste. A default isn't a force that pushes your choice. It's just the direction you get if you do nothing. If something bothers them, people will gladly open settings.
That's why this force weakens in two cases. One is when the outcome really matters. If a big sum of money is on the line, you'll check even the pre-checked boxes one by one. The other is when changing is very easy. If it sits on the first screen as a single button, the hurdle gets lower.
So what to make the default is a choice for the people who design the product. If they set the default to what benefits the user, it works as a gentle help, and using this kind of tool that way is called a nudge. If they set the default to what benefits only the seller, it becomes a trick that quietly shifts the cost onto the user.
Common misconceptions
People leave defaults alone because they're lazy.
It's a natural response to having limited attention and time. On top of that, a default can also be read as a recommendation that says "this is what people usually do."
You can change it anytime anyway, so it doesn't matter what the default is.
Even when changing is possible, not many people actually do it. That's why the overall outcome can differ a lot depending on which way the default is set.
Where you meet it
If consent to receive ads is pre-checked on a sign-up screen, many people click through without reading it.
If autoplay is on from the start in a video app, you end up watching the next episode without ever turning it off.
In one sentence
People tend to go along with whatever is pre-set, so where you place the starting point can change the whole outcome.