Is it a dark pattern to change Radio buttons into a Dropdown in order to default to a particular option? The default option is the best deal and recommended for the user. However we still want to keep the other options. One idea was to not make all the options visible at first glance by hiding them within a select box so that more users choose the recommended option.
First, radio buttons can have a default. So, at issue here isn't the fact that a dropdown affords you a default selection and radio buttons don't. What you are doing by switching from radio buttons to a dropdown is hiding the other options from plain view.
- If you are using a dropdown list to hide options from users because you've assumed they want/need a certain thing, then you might be making the UX worse by hiding the available options and making users go through more hassle to find what they actually want.
- If you are using the dropdown list to hide options from users because you don't want them to choose those options (and you're justifying it to yourself/your boss/us by saying that option is "the best" for your users), that is definitely a dark pattern.
At the core of user experience design is user research. You need to make decisions based on your understanding of the goals, needs, and contexts of real people when they're using your design. In your question and in your comment on another answer, you've said that you'd like to have a default option because "the recommended option will benefit the user more than the other options." Unless you have come to that conclusion by interviewing and studying the real people using your product, that is an assumption (at best). Basing designs on an assumption is risky; using designs to manipulate users into choosing what's best for your business (but not necessarily for themselves) is where it becomes a "dark pattern."
Are you doing this with the interest of the user at heart or are you doing this to benefit the business?
If the default option is the best for the user, then hiding the other options in the dropdown is beneficial and thus not a dark pattern.
Conversely, if the selection is for say payment packages and you put the most expense one as the default and hide the rest of the cheaper options in the dropdown, then it's a dark pattern.