When the impact of "Culture" on behavior and developmental trajctories is investigated, I often find studies which compare samples from different countries which are presumably representing different "Cultures", for example, how is X different in country A and country B. However, it is not totally satisfactory to assume that the samples represent relevant cultural differences just because they come from different countries. And, in addition, the question of how would one detect different "cultures" within a country could not be addressed with a valid rationale.
Therefore my question: What would be a valid instrument for measuring "Culture" to validate cross-cultural research?