The term mental model has its roots in psychology. It refers to someone’s thought process about how the world works—their frame of reality.
Mental models allow us to predict how things work. They are cognitive constructs built on beliefs, assumptions, and past experiences. But a person’s mental model is a perception of a how a system functions, not necessarily how it actually may work.
For instance, say you come into your house on a cold day. To get warmed up quickly, you turn the thermostat way up. Your assumption is that the higher thermostat setting, the more heat will come out.
But a thermostat does not work like a faucet valve. It’s more like a switch: the heat goes on or off depending on set temperature (see Figure 12-1). In this scenario, you’d have a wrong mental model of how the system actually works. The room won’t get warmer faster. Instead, the heater will simply stay on longer to reach a higher temperature.
The lesson for providers of products or services is profound: your understanding of the systems you create differs from the user’s understanding. You have far ...