Ask HN: What is a YC Research interview like?

Has anyone done a YCR interview that can share what it was like? I got an email this week that said it's a 5-minute Skype call, with no further context. What can you do in a 5 minutes? I have a pretty good sense of how the 10 minute YC "core" interviews work based on the many blog posts about them and a few friends who have gone through the program, but I can't find anything about YCR.