[She looked for something to relax against. This might be a long conversation. The first question, though, was logical and simpler.]

We don't know. Most of the time, something triggers it. Seeing a gun might cause you to see a vision that involves guns. Looking into a campfire might show someone something of a fire, or campaign. I was in a water gun fight when I remembered something once.

[She sighed, raking her fingers through her hair.] But it isn't guaranteed. Sometimes it's ... just random. No warning, and Retrospec once offered to just give people one if they won a contest.