🍜 Default Bias:
We tend to accept the option pre-chosen for us
Amazon
Default options in checkout
Without a compelling incentive to change, people tend to stick to the default suggestion, option or product.
In short: making a decision usually requires effort, and it's easier for them to just accept the default option.

Nudge theory:
The behavioural science theory of 'nudges' is based on the understanding that people can be encouraged to adopt healthier habits, just by changing default options in their lives.
For example, placing unhealthy snacks further away than healthy ones will lead to less consumption of unhealthy food.
Think of 'nudges' being a way to counter the default bias.
✅ Conversion rates
Having a suitable default option can encourage people to convert down a particular path.
✅ Feature usage
If a feature is turned on by default (or is included in onboarding), it may be used more than if the user has to proactively turn it on.
This is also true if using a feature is the default option (i.e., if sending an SMS message is the default, rather than a WhatsApp).
✅ Purchases
The default package (i.e., pre-selected) is often bought disproportionately more.
✅ Habits
It's easier to adopt a habit if the user doesn't have to proactively make lots of decisions.
✅ Productivity & efficiency
People will be more efficient at a task, if suitable default options are used. e.g., auto-generating usernames based on the user's real name.
✅ Effort & motivation

When browsing for 'repeat goods' (e.g., dog food), Amazon will have their default option as 'subscribe and save'.
