I get many variations on this question, "Are interviews the only way to build a mental model?" The answer is no, interviews are not the only way. There are many sources you can analyze, some of which are even richer than non-directed interviews. Here are some ideas. (Please comment if you have additional sources to mention.)

Rich Data Sources

• Non-Directed Interview
• Contextual Inquiry
• Ethnography
• Field Study
• Retrospective Review (with video)

Data Sources Requiring Inference/Guesswork

• Customer Feedback
• Call Center Recordings
• Diary