Should a required SELECT have a placeholder OPTION?

Question

I have a small form for a search function. There is a "Search By" select in the form and, depending on the option selected in "Search By", a related "Search For" select is generated with respective options.

Both of these select fields are required for the search. Is there any reason for the select have have a "placeholder" option with an empty value, displaying placeholder text like, "Please select a value"?

Since the field is required, it seems like this forces, perhaps, unnecessary clicks, however if the fields are defaulted to legitimate values, the user may not realize more options exist to filter the search.

Answer 1

If the field is required, it should not be auto-filled, because

Fields with stuff in them are less noticeable.

Eyetracking studies show that users’ eyes are drawn to empty fields. At the minimum, users will spend more time locating a non-empty field — a nuisance. At the worst, they will overlook the field completely—a potential business-killing disaster.

Read more on Placeholders in form fields are harmful

Answer 2

Really, it has nothing to do with whether it's required or not. The nature of a select box is that something is always selected, whether that be a placeholder (which is still just an option like any other) or one of the actual available options.

Given that, the only acceptable time to exclude a placeholder is when there is a valid default option for the select box. For example, a country select box, may default to "United States" for an American website, since that's the most common choice for its users. In that case, no placeholder would be necessary. If there's no default option that makes sense, then the default should be the placeholder option.