For years cultural knowledge has been likened to grammar.
People learn it automatically as they grow up, and can deftly use the rules inherent in it.
However, though they presumably have models in their heads about many things, they often can no more describe these models than they can the rules of grammar. In his chapter he goes on to describe how he was able to listen to undergraduates talk about the human mind and then make explicit their unconscious model. This is one example of the interpretation of qualitative data. The literature below contains many others. How to Grow Schemata out of Interviews.