I think that one of the best examples of exchange through spatial interaction is culture in all it's varieties. Be it food, music, language among others. When migration occurs, there is a exchange between two or more cultures, which leads to a fusion of customs innate to different types of population. Let's take peruvian cuisine as an example, it's so rich and so varied that we might overlook that it has strong influences from japanese and mexican cuisine, and we can all be grateful for that.