It looks like you can explicitly exclude attributes from the parent or the association or both. Here's an example directly from the docs:
pirate.dup :include => :parrot, :except => [:name, { :parrot => [:name] }]
For your case, you'll want to leave off the :name of the parent like this:
pirate.dup :include => :parrot, :except => [{ :parrot => [:name] }]
As an aside, you can also include attributes from just the association, which could serve your needs just fine if you want to use a whitelisting technique. This is the example directly from the docs:
pirate.dup :include => :parrot, :only => [:name, { :parrot => [:name] }]
What you probably want to do for whitelisting is this:
pirate.dup :include => :parrot, :only => [{ :parrot => [:name] }]
Hope this helps!