Principles of Interaction Design

Designing Conversations

Interaction design (IxD) is about how a product behaves when people use it: what happens when they tap, type, swipe, wait or make a mistake. Visual design makes a screen look right. Interaction design makes it feel right.

Every interaction is a small conversation. The user does something, and the product responds. When the responses are clear, quick and predictable, people trust the product. When they are not, people tap three times, abandon their cart or call customer support.

Many of these principles come from Don Norman's classic book The Design of Everyday Things and Jakob Nielsen's 10 usability heuristics, which are still used by design teams worldwide.

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1. Feedback

Every action should get a visible response, quickly.

• A button changes when pressed.
• A spinner appears while a transfer processes.
• A success message confirms that the airtime was sent.

Response time guidelines:

• Under 0.1 seconds: feels instant
• Around 1 second: the user notices the delay but keeps their train of thought. Show a pressed state or subtle indicator.
• Over 10 seconds: show progress and let them do something else

In Nigeria, network delays are common, so feedback is critical. The dreaded "Did my transfer go through?" moment leads users to try again, sometimes paying twice. Clear pending states and receipts prevent this.

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2. Affordance and Signifiers

An affordance is what an object allows you to do. A signifier is the clue that tells you it is possible.

• A raised, coloured button signifies "tap me".
• Underlined blue text signifies a link.
• A handle on a bottom sheet signifies it can be dragged.

Flat design removed many signifiers, and usability suffered. If users cannot tell what is tappable, they will not tap it. Make interactive elements look interactive.

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3. Consistency

Similar things should look and behave the same way.

• Internal consistency: the "Back" action works the same way on every screen, and primary buttons are always the same colour.
• External consistency: follow platform conventions. Android users expect the system back gesture. iOS users expect swipe-from-left-edge to go back.

Consistency means users learn once and apply everywhere. It is one of the biggest benefits of a design system.

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4. Error Prevention and Recovery

The best error message is the one that never appears.

Prevent errors:

• Input masks and formatting (a phone field that accepts only numbers)
• Sensible defaults
• Disable impossible choices, or better, explain why they are unavailable
• Confirmation for destructive or irreversible actions: "Send ₦250,000 to Chidi Okeke (GTBank)?"
• Showing the account name after a user types an account number, which Nigerian banking apps do very well and which prevents countless wrong transfers

Help recovery:

• Clear error messages in plain language: what happened and how to fix it
• Undo where possible, which is often better than confirmation dialogs
• Keep what the user typed. Never clear a long form because of one mistake.

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5. Other Principles Worth Knowing

• Visibility of system status: always show where the user is and what is happening.
• User control and freedom: provide clear exits and cancel options.
• Recognition over recall: show options instead of making people remember them, for example recent beneficiaries.
• Fitts's law: bigger and closer targets are faster to hit. Put key actions within thumb reach.
• Hick's law: more choices mean slower decisions. Keep menus focused.

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Try It in the Lab

The lab shows four interaction patterns, each in a bad and a good version. Try the bad version first and notice how it feels, then switch to the good one. Each card explains which principle is at work.