People think in symbols but the symbols in our mind are not the actual objects themselves. That is to say: when you think of an apple, that apple is not real. This is the treachery of symbols. The symbols in our mind don’t always match the reality of an object. We think we know how to use an object based on the symbol in our mind that we apply to it.
This leads to encounters with objects like this:
We automatically interact with an object as if we know what the object is based on the symbols in our mind. It’s second nature.
This object is perfectly functional: push on the top; liquid squirts out. But good design isn’t just designing an item that functions. It’s designing for expectations. No matter how well designed a widget may be, people expect certain things in certain contexts. They expect certain interactions to produce certain results.