Frame 3: Minimise interaction cost

Ask: what does this cost the user, counted?

Interaction cost is the total physical and mental effort to complete a task: clicks, scrolls, pointer distance, keystrokes, waiting, reading, and anything the user must remember or go and find. Its virtue is that it is countable, which makes it the most checkable idea in this file.

Three reliable reductions:

1. 1.
   Keep related actions close, and targets large. Per Fitts's law, time to hit a target falls as it gets nearer and bigger. Put the action beside the thing it acts on; keep targets at --size-touch-target or larger. Start-aligning the action also keeps it visible to screen-magnifier users.
2. 2.
   Cut distraction. Banners, autoplay, unsolicited dialogs — cost charged against a task the user did not choose to pause.
3. 3.
   Cut choices. Per Hick's law, decision time rises with the number and complexity of options. Fewer options, or a promoted recommended subset, produces faster decisions.

Use it like this: count before and after, and state it. "3 clicks + 1 scroll → 2 clicks" is reviewable. "Improved the UX" is not. See P-10.