You can perhaps think of interviewing as a tree structure, branches being created or ended as different questions and responses are explored.

Using the FBI Interviewing Method as previously discussed will help you mentally build this tree, and also move between the branches effectively.

Example
During a usability playtest, the player’s inventory becomes full and the player manually sells items one by one, despite the game having an auto-sell feature. Did the player not use this feature because they weren’t aware of it, or because they chose not to use it? Going into the interview, you know you will end up discussing the auto-sell feature one way or the other, The FBI interview framework will help you get there.

Mode 1 - Fundamentals
Interviewer: “What is the main goal in this game?”
Participant: “I think you have to defeat the evil overlord of the kingdom.”
Interviewer: “And how do you go about doing that?”
Participant: “You have to collect resources and upgrade your skills by completing a series of increasingly difficult quests.”

Mode 2 - Bridging
Let’s assume the player mentioned inventory in the Fundamentals section of the interview, we’re going to use their own awareness of this feature to bridge the interview to the section we’re interested in. 
Interviewer: “Earlier you mentioned your inventory, tell me how that works.”
Participant: “When you collect items in the game you store them in your backpack. The backpack looks small on the player character but you can actually store quite a few items in it. Having said that, it was nearly always full and I had to constantly go in to free up space.”

Mode 3 - Investigating
Interviewer: “How did you go about freeing up space in your inventory?”. Here we’re starting to explore the player’s mental model of how they think inventory management works.
Participant: “I would first look for items to sell as I could then use the money to upgrade my weapons and armour. Such items would be typically be grouped together so I could sell them one-by-one.” 
Interviewer: “Did you have to sell them one-by-one or was there a way to speed that up?”
Participant: “Yes, there was an auto-sell feature that could speed it up.”. It seems the player is aware of the auto-sell feature but chose not to use it, why is that? 
Interviewer: “How come you didn’t use the auto-sell feature?”
Participant: “I wanted to learn more about the value of each individual item, rather than the value of all the items combined. Maybe later in the game I’ll use the auto-sell feature once I have a better understanding of how much each item is worth.” 

If the player had not been aware of the auto-sell feature, we might have taken a different ‘branch’ of the interview tree which explores the player’s understanding of auto-sell features in other games, is this something they’re aware of generally?

Ultimately we’re trying to investigate if the player is aware of the feature, if they understood what it is for, are they able to use it, and whether or not they are motivated to use such a feature.

Key Takeaway

A tree structure is a useful mental model for exploring the player’s mental model. Using the three modes of the FBI interview method helps you build this tree and move around effectively.

Next: 52. Interviewing - A Checklist