Response tokens
Non-response
One sub-set of studies of response-tokens involves studies of their omission: response-tokens withheld in instances of 'non-response'.
This list is based on responses to Isobel Ross' thread about withholding of response tokens withholding of response tokens on the languse mailing list.
In that mail she asks: "I am looking for any research that specifically addresses the withholding of or lack of response tokens (such as continuers and acknowledgement tokens) in conversation (mundane or institutional)."