A. studies 'tag declaratives' as for their functions in conversation. Tags of reversed polarity (e.g. 'it is time for lunch, isn't it', 'it is not time for lunch, is it') are said to (chiefly) check the hearer's acceptance, confirmation, interest, etc., while tags of constant polarity (e.g. 'it is time for lunch, is it') are used (primarily) to check the validity of one's own understanding or inferences.