Fitt’s Law

This law is a predictive model for how a user will move in a human-computer interaction. It states that the time to move quickly to a specific area is affected by the distance between start and finish and how large the target is.

Hick’s Law

Sometimes referred to as the Hick-Hyman Law, this law outlines the amount of time a person will need to make a decision. The more possible choices they’re presented with, the more time it will take for them to make a decision.

Jakob’s Law

This law states that web users prefer new sites they visit to act in a similar way to other sites they use. The familiarity makes the new site easier to use.

Parkinson’s Law

An amusing principle that states that the time to complete a task will expand to fill the time given. For example, if you’re given a day to do a task that should take one hour, it will end up taking a week to complete.

Postel’s Law

This computing theory is a guideline for software design, where ideally you’re being conservative in what you present, but liberal in what you accept from others.

Principle of Habit Formation

If a user repeatedly uses an interface, they’re likely to develop a habit for this usage. When designing, you should therefore try and encourage “good” usage rather than bad habits.

Principle of Least Astonishment (POLA)

This principle states that when you’re designing an experience, you need to remember that human beings can only pay full attention to one thing at a time, meaning that you should reduce the amount of new things you introduce at once.

Tesler’s Law

Also known as the Waterbed Theory, this is the “law of conservation or complexity”. This theory states that every human-computer interaction will involve some amount of complexity, which can’t be hidden away or cut out entirely.