one more answer with thanks

[Annette Karmiloff-Smith]

Were you looking for studies on tag questions?  I happen to be reading a
paper by Rice and Wexler (1999) that discusses a paper by Weckerly,
Contreras, Wulfeck, Bellugi, and Reilly (1997) on acquisition of tag
questions and grammaticality judgments, pertaining to "agreement of the tag
auxiliary verb form with a subject pronoun, tense, and polarity".  I don't
have your original message requesting references, so I hope that this is
indeed relevant.