Becareful with the interviews that seem like a casual conversation. Some interviewers want to see how you go with the flow. They want to read your reactions and see how you conduct yourself in that setting. You see this during residency interviews too. Some places specifically have one interviewer that will always be serious and critical, while another interviewer will be causal.Two weeks ago, I had an interview that was absolutely pointless. If you had started a stopwatch every time that I started speaking, I think you'd come up with the figure of me talking for about five or six minutes (out of a thirty minute interview). My application was just one big segue for my interviewer to launch into another humorous anecdote of his. Asking me about my hometown, for example, served simply as a chance for him to point out that, as a respected researcher in his field, he was invited to a conference near my town. And so on.