Everyone thinks they understand what’s happening.

They don’t.

That’s part of what makes Modern Family work. One person assumes they understand a situation, another person interprets it completely differently, and both act according to their assumptions.

The result?

Chaos.

UX has a surprisingly similar problem.

Designers know. Users don’t.

Designers understand how the product actually works.

They know the system logic, the business rules, the technical constraints, and what happens behind the interface.

Users don’t see any of that.

Instead, they create their own explanation:

“This is what I think this does.”

That explanation becomes their mental model. 

And users don’t interact with your product based on your intentions.

They interact based on what they expect will happen.

When the interface confirms that expectation, users feel more confident.

When it contradicts their expectation, confusion, hesitation, and mistakes can follow. 

Think about a simple profile edit

A user changes their name and leaves the screen.

There is no obvious Save button.

There is no confirmation.

What might they assume?

“It probably saved.”

If the system doesn’t actually save the change, the problem isn’t necessarily that the user was careless.

There is a gap between the user’s mental model and the system’s behaviour. 

So how do we design for this?

Don’t try to teach users your mental model.

Instead, make the correct mental model easy to form.

Use:

• Familiar patterns
• Clear labels
• Visible feedback
• Predictable behaviour 

A useful usability-testing question is:

“What do you think will happen when you click this?”

Then watch what happens.

If their prediction doesn’t match the actual behaviour, you’ve found a mental-model gap.

The Mental Model Audit

Before shipping a flow, ask:

Expectation — What will users think happens?

Familiarity — Does it build on patterns they already know?

Language — Are we using words users understand?

Feedback — Can users tell what changed?

Predictability — Does the system behave as expected?

Testing — Can users accurately predict what happens next?

The goal isn’t to make users understand your system.

Your job is to reduce the gap between the designer’s mental model and the user’s mental model