The follow-up
Stay with the answer long enough to understand it.
In conversation
A prepared question list is useful until it prevents the interviewer from listening. The follow-up is where the conversation can become specific.
Participants practise returning to a decision, a sequence or a claim in an answer. The aim is to invite an explanation without supplying the explanation for the speaker.
Review focuses on the information gained. A longer conversation is not automatically a better one; a useful follow-up helps establish something relevant to the purpose of the interview.