... In many cases, these domains require very specialised, *accurate* mental models of their users, because the domain is just complex. They can be only a simple as possible... but no simpler. Many #BigTech apps make things 'too simple', glossing over technical complexities & user conceptual competence, which is why we have computer viruses & malware among other issues plaguing modern computer users. It's also why many fear computers: their mental models are invalid, offering no guidance. 3/n