One technique they use to get people to explain narratives are Story Cubes.
These aren't typical cubes, instead they are have 12 faces, so each cube can tell two different stories.
Respondents then use the cubes to describe their narrative. They can create multiple cubes to create multiple stories or simply create stories that are linked together through the cubes.
"Like books turned inside out and upside down they are read by turning and twisting in your hand and combining in vertical and horizontal constructions; adding a new dimension to what we now think of as interactivity."
So instead of using collages, at your next focus group, you should go for cubes. They are simple, clear and allow a story to be told.
Perhaps you can use these for creative briefings?
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A story in a puzzle with a lot of blank space for imagination. I will definately try this one on my next briefing. What a surprise for the creative minds...