If I have the following:
I guess either the registration scope is not initialized or registration.first_name is an object.
Have a look at this plunker: http://plnkr.co/edit/bdbs0XVB8hZSodOTYyM4?p=preview
Initialize the registation model either in controller or using ng-init ng-init="registration = {}"
If registration.first_name is an object then this will be displayed as [Object object]
. You have to supply a proper string value as model to the ng-model