Every culture and subculture shares mental models of how the world works. From an understanding of how to use the public transportation in a particular city, to how to order coffee at Starbucks, to how Google search works.
Users bring to your product an expectation of how it will function, based on their own mental models. Product designers try to understand what those models are when designing new products or applications.
Many of our mental models overlap. Starbucks customers in the US know what a Grande Latte is, and that they must order and pay for the coffee before they pick it up from the barista. But if you don’t live in the US, or you don’t buy your coffee at Starbucks, you may have a different mental model about how to buy a cup of coffee.
Even within much smaller cultural groups — say a city or community — mental models differ. When I first moved from NYC to San Francisco, I found the difference between how the NYC subway worked and San Francisco subway confusing and frustrating. My mental model of a subway system overlapped enough with that of San Francisco’s so that I could figure out how to use it. But I had to learn entirely new customs (for instance, why do BART riders all line up before entering the trains? It’s not efficient.) Those differences made my first few weeks of using BART painful, and I wouldn’t have kept at it if I wasn’t forced to.
Anyone that has grown accustom to buying coffee at Starbucks, then bought one at Phils will experience the same confusion and frustration. As product designers, we try to eliminate painful mismatches between mental models so our users will keep using our products.
The first step in any design process is to understand your users. That means learning how they see the world, and working within their expectations. If you don’t, your users won’t want to use your product.