From Measuring Usability:
Usability is hardly physics or chemistry. But there are some important principles from decades of research in Human Computer Interaction (HCI) that apply to design and user research.
Read all about it: Five HCI Laws For User Experience Design
- Miller’s Law of Short-Term Memory Load: People can only hold up to about 7 pieces of info in short-term memory.
- Fitts’ Law: Users will hit a target faster if it’s big and close to where they start.
- Hick-Hyman Law: Users will take longer to decide if you give me heaps of choices.
- Power Law of Practice: Users do stuff faster the more they practice.
- Pareto & Zipf Laws: The 80/20 rule – the majority of stuff will be addressed by a minority of things. (Eg. “A small portion of our site gets hit by a majority of our users.”)
Link via @higroup