Boolean method parameters are a code smell.
The are meaningless und should be avoided. However there are rare cases, where an API expects a boolean parameter.
Some of the view helper methods in Ruby on Rails are defined with a boolean parameter signature. For eample there is check_box_tag. The third parameter is a boolean and has to be set to true explicitly for checking the check box:
check_box_tag 'user[notified]', 1, true
The checked box:
Though the meaning of the third parameter has to be known well for understanding the source code properly. But passing a truthy value instead of true, the meaning gets obvious:
check_box_tag 'user[notified]', 1, :checked
Boolean parameters always can be approached like that, if the defined default value is false.